Thanks for advice, we tried this option, it works.
But there is a case, when you animate two characters and you want to synchronize the animation of one character with another, it was convenient in version 3.6 when you select the skeleton of one character (without hiding another), you'll see the moves of both characters(on main window or preview), but you continue to work with the keys of selected character.. and if you need to find the keys of the second character, it was enough to click on the second character skeleton. (more convenient than now).
if it's difficult to change something as an option such pop-up window (image3) would help us a lot.
Thank you very much for your attention.