In the Roblox Studio Explorer panel you can left click and drag in order to select multiple objects, However, when you right click while you are using the selection box then it literally freezes there and won’t disappear until you close the place and open a new one or restart studio. It’s a very minor bug, but it would be nice to see it fixed soon.
From my experience it happens every time when the explorer panel is usable.
Here is a video I made sometime ago displaying the bug.