Workout screen (how to edit?)

This is not the point of the issue. The workout screen has a standard screen for pre-uploaded workout. If you set an average pace to keep for 10 km, you will see a bar indicating if your pace is in the range or not. With previous models, in training sessions with pace target, the indicator worked with the average pace, in 965 it works with the instant pace (and obviously you get the alert from the watch when your instant pace is out of range)

I hope this clarifies the problem

There are clearly two opinions on whether workout step pace targets should use lap average pace or instant pace. If you search this forum, the older watch models have lots of threads complaining about using average lap pace and requesting instant pace as target. So Garmin has clearly made a conscious choice to change it (probably because instant pace has become a little more reliable lately).

I think the solution would be to have both as possible workout step targets. People would still complain, because automatically created workouts would still have to use one of them, and some would be unhappy no matter which one they chose.

Thats by FAR the best answer on this subject I have seen so far

But question is… what cost to Garmin to give this option and why they havent done it until now?? I would guess it is reasonable easy for them to allow the choice

I'm not sure you are going to like this answer as much (and it's of course only a guess), but here goes: Adding customization options is not totally free in software engineering. The amount of additional code is probably small, but it makes the code more error prone and testing more complicated. Options might unintentionally affect each other, so you would have to test all their possible combinations, and the number of combinations explodes too large really soon. And considering how many bugs Garmin has to deal with now already, I understand they are reluctant to make introducing new bugs easier and more difficult to test. And it's not just this one wish for additional configuration, these forums are literally full of similar wishes with other features.

Also, if you read Garmin watch reviews or even this forum, it's clear that the number of current configuration options in Garmin watches is already so huge, that reviewers complain about it and people no longer even consider consulting the watch manual. So again, adding more configuration options would (in addition to potentially solving this problem) also make the watch even more complicated to use, and require writing more documentation (that no-one would still read, I guess). Even now the Garmin documentation is lacking, so... And without documentation, we would get loads of questions like "hey, why on earth are there two ways to set pace targets for a workout, which one should I use and why doesn't Garmin tell me which is better" and "why in the world does Garmin have to provide two options, it's so easy to miss-click, and nobody on Earth would want to use lap average pace / instant pace as a target (choose the one you don't personally like)".

So again, I'm with you in that I (personally) would also like there to be two options. But at the same time, I completely understand why Garmin might choose not to provide the choice. They have to make a compromise. I'm already surprised they decided to make a change in how pace targets work in newer watches, because (as you can see here), any change annoys those who liked it better before (and of course those who like the new way more are glad).

Here's a quote I once found (cannot remember anymore where), which is surprising fitting in many contexts: "Good engineering involves compromise at every turn. ... The art of good engineering is to know what your options are, and then to choose your trade-offs wisely."

Do I hear a wish for a third workout target option: grade adjusted instant pace? 

I totally agree with you. It is a compromise decision that was taken from software engineering prospective. My (and many other users) opinion is that this decision is not the most efficient especially if we talk about the most advanced watch of the series (supposed to be used by advanced runners) this is because:

1) Instant pace is by definition not accurate, because of data processing time. There will be a delay between data reading and effective speed measure

2) If my target is to run 10 km at 4 min/km, my focus is not if for 10 sec I am running at 4:10, but if my 10 km average is within the range. This is especially true in case of hills along the way, or if we set this pace target for a race

3) instant pace data field gives you an estimation of the pace (with a sensitivity of 5 seconds/km). The average pace had a sensitivity of 1 s/km or s/mile. So, again it is less reliable/precise

so obviously anyone can have different preferences, but fore sure instant pace measure is less reliable than the average pace. The real question is then why Garmin introduced this less precise feature in the most expensive Forerunner?

On a more serious note, I found average lap pace target (that I had on my old Fenix 5+) to be somewhat problematic also. I'm also living in a somewhat hilly area. Let's say I wanted to do a 1 hour base run with a certain average pace target. Then, if my route started uphill, I would probably run slower and let the average pace drop near the lower limit. But then, when my route starts going downhill, I don't know any more how fast I run (unless I change to another screen), or how fast I should keep my pace in order to correct the average before the next uphill (and I would have to know whether there's another uphill on the route I should prepare for to keep the average within limits). This is of course why Garmin added Pace Pro on many watches.

But when I changed from Fenix 5+ to Forerunner 965, I didn't find the new instant pace target any more or less problematic than the old average pace target. They are just differently problematic.

It just occurred to me that one reason why Garmin might have decided to do the change could be the addition of Execution score to the workout. With average pace targets, it doesn't make much sense to keep score on how much of the time you were within target limits, because at the beginning of the lap the average fluctuates much more than near the end of the lap.

While vaguely interesting it's not something I'd care about. If I've a target pace for a 10k race then it would be good to know at the 9k mark how I'm doing overall with my target. 

I understand, and it works for that use case. But actually, that's also why for other uses it's less valuable: The target is not actually "average lap pace", it's "average lap pace so far" = "time so far / distance so far". Let's say I'm doing a daily suggested base workout (which I do regularly) with a pace target. Then I'm trying (more or less, depending on terrain) to maintain that pace to keep the workout as base. "Average pace so far" doesn't help there much later in the run, because it doesn't tell me anything about how I'm running now, just how my average progress from start to that point has been.

So, and in all seriousness, there are at least the following pace targets that have real uses (or at least people who want to use them):

• Instant pace (as instant as it can be, useful for short intervals)
• Grade adjusted instant pace (also lags a little, since GPS pace and barometric altitude are not instant, useful for "am I in the right zone")
• Average pace so far (discussed already)
• Average pace for the last 3 sec / 5 sec / 10 sec / 30 sec / 1 min / ... (smooths out small hills and other fluctuations)
• And maybe the grade adjusted version of the above

Reading the above, I completely understand why Garmin is reluctant to add more options (especially since the fourth item contains as an additional parameter the width of the averaging window). The pace target choice would have to be available when you create each lap the workout (because for an interval workout, different steps might have different kind of pace targets). And you can create workouts on many of the watches, Garmin Connect Mobile, and Garmin Connect Web (that's already at least three different softwares). And if all watches wouldn't get these at the same time, you would have to decide if you have to first select your watch before creating the workout (to find out what targets it supports), and what to do if you try to send a workout created for one watch to another that doesn't support the same pace targets.

Call me stupid, but as much as I'd like all the configurability, I cannot blame the software team managers who are not eager to open this can of worms... Even if we are not talking about all the options I listed, but just some of them. It has to be some kind of compromise. I'm not saying the current one is the best, but it's "one".

Often this all boils down to the fact that we all (myself included) wish for a watch that would be perfect for my needs and wishes. But Garmin has to create devices and software that's "good enough" (or close enough) for everyones needs. Or at least for as many as possible, whatever that means. Unfortunately.