How to convert Move IQ Event to proper workout?

They should make it possible 

Frankly told, it would not make much sense, since most of the data is not available. Data like detailed HR, GPS track, LTHR, VO₂max, HRV, RD, TE, ... are being recorded only when you start an activity, which means you cannot retrieve the data retroactively.

However, I understand that for your records you may be willing to have that activity logged anyway. You can still create the activity manually. You are right that the possibility to use the MoveIQ event would simplify the task little bit, but such cases should be relatively rare, so creating the activity manually is still a good solution.

Consider suggesting it to Garmin: Share Ideas | Garmin 

I vote yes to at least make this option available.  

It would benefit 1st time users or users who purchased a new device.  Also, there are times when you just forget.

Thanks for considering. 

They should make it available even if all the data isn't recorder is far better than just a manual activity with only time duration.
I've walked the whole afternoon yesterday and I regret that I have forgotten to start a walk activity.
I can see a Move IQ Event but can't don nothing with this unfortunately.

You can create a manual activity with the data you see in the Move IQ event. Or if you want it to count towards challenges you can log a 1 second activity on the watch, save and sync and then edit that activity with the correct data. 

Garmin does calculate a recovery period for a move IQ event. This does suggest that an exercise load is determined.

However, the activity is just ignored and not even added to the active training load - unfortunate. Wouldn't this lead to a distorted picture of training load vs progress? Definitely, a good fix to have.

How do you know that a recovery period is calculated for Move IQ events? 

you can check on your watch after recording a move IQ event.

Go to Training status with the button at 7 o'clock  (I have a Fenix 6 pro) press the enter button at 2 o'clock and scroll down with the button at 7 o'clock...

This is what Garmin says about it: "Recently, recovery time has been improved by introducing health and lifestyle tracking data to the analysis for the first time. This means that on compatible Garmin devices, all-day stress tracking and estimated sleep tracking data is now used to increase and decrease your recovery time recommendations, and the impact of your day-to-day activities is now also factored into the equation to complete the picture."

https://www.garmin.com/en-US/garmin-technology/running-science/physiological-measurements/recovery-time/ 

Everything you do will be used to calculate the recovery time. Not just Move IQ events.

Turn off Move IQ and see if you get the same affect on recovery time.

If you think that the training load will be distorted without the Move IQ events then start to log them as timed activities. Or at least do a test a few weeks with that and see if it makes any real difference.