It's a really simple thing that causes endless frustration working with AGS: if open an "add sprite" (to a view or GUI control) dialog while the sprite tab is open, it collapses any folders you have expanded in that tab.
This makes it very tedious to perform tasks that involve checking the contents of certain sprite folders and adding them to different things. If someone could fix it, I'm sure it'd save endless wasted hours in total for all AGS devs.
When that window is closed it is calling spriteController.Refresh();...in case a sprite was added in the selector. I'll take a look at it.
This was fixed.