Hi, yes you got it right.
Yeah there isn't a way Would be a time saver to have that option though (just in my opinion, well not for all the users).
Let's say you do an in place walk or run cycle or an animated creature tail, sometimes it is just happen to have some keys outside the animation range just because you set the animation curves to "infinity" in Maya or add the "Cycles" modifier to a curve in Blender which makes the curve to repeat to infinity. If you offset the whole curve to achieve some drag/overlapping, the keys would go outside the range. Yes i could go and add keys inside the range but the whole idea is that often you need to go back and change or polish animation clips. In this case you have to export one by one all the actions with the proper range set, and then import them one by one in a new blender project in order to have animation actions with proper range ( this is what i have done in order to have proper animations in sketchfab ). Now when i go back an polish or change some animations i will have to export the takes and do that part of the process again before update a model to sketchfab. Not always when you upload a model for first time it will have the best animations.
Another example for having keys out side the range is if you have a walk cycle and animate the one leg only, you can just copy all the curves to the other leg and then in the graph editor you offset the keys in order to offset the other leg (because it moves exactly to the one from which we copied the curves), this is much faster way of animating a walk cycle and i use it but i very often decide that i need to polish something and if i want to have the updated animations in sketchfab i have to export and import in new project and compose them again.
If i had the option to set a range per animation take in sketchfab i will just export the FBX after i am done with animations and when i re-upload it to sketchfab it will be updated without the need to go through this tedious process in blender.
The Unity engine has exactly the option that i am pointing - you can set the range from the take you want to use !
I would guess that many users would benefit from such option in sketchfab.
If you consider adding such an option would be awesome... and may be ask the users if they would need it !
Thanks. Currently i found the way to prepare an animated model for sketchfab. Thank You !