How Do I Arrange My Extensions?

I have many extensions/add-ons.  I need to have the ones most used to the left so they do not disappear when I resize my browser horizontally, for example, Lastpass.  I can find no mention of arranging them but when I left click and drag an extension, it changes to an insertion and the other "icons" seem to move to make room.  But when I release the drag, the one I was dragging has not moved, but is now a blank space.  If I hover over it, it is still there but invisible.