To formally request this feature, please use the link below:
It sounds like a feature request. Share this idea with them: https://www.garmin.com/en-US/forms/ideas/
This is crazy that this has been here for 3+ years and is an obvious easy area for improvement - as they have added all these different categories and I can't even tell it a default for mountain biking…
I find it hard to believe that something so simple to implement and so obviously useful to riders who, for example, want to set different default bikes for mountain biking vs. road biking, isn't implemented…
Hiking shoes to hiking
Running shoes to running
That's already possible, and as far as I remember, always was.

Even perhaps different bikes to different kinds of biking
Please request it at https://www.garmin.com/en-US/forms/ideas/ to give it bigger chance to be considered by Garmin
Yes because running and hiking are 2 different main activities , try automatic assignment on trail run or track run and you are done. same with cycling.
ideas link is not helping, you can write there as much as you can. Total ignoration.
At least Strava understood and did it automaticaly recently.
For garmin apparently morning report and nonsense like that is more important.
There are different running activites...so the generic "Running" isn't helpful. There is:
There are 14 for Cycling. I'd guess the majority of people are have multiple pieces of equipment depending on what they are doing. Personally I have 3 sets of cycling shoes, one for road, one for indoor, and one for mountain biking. So it's a pain point.
TTBJaap asked specifically for Hiking and Running. That's possible. Subcategories are not available, which is well known, and the topic of this thread, mentioned hundreds of times here, so I do not think it is necessary explaining it again. That's why I suggested requesting the feature through the form Share Ideas | Garmin, where it has a better change to reach the developers than here, on the forum.