even better (or in addition) would be to make that dialog box window resizable (mouse drag) or at least make it 3-4x taller.
There are 94 buttons available before moving any to a toolbar.
Seeing them 7-8 at-a-time is a pain.
Fortunately, setting up toolbars is not going to be a daily activity (once I settle on just what I want).
I'll add a vote for a sortable and/or resizable "Customize Toolbar" dialog.
Also, is it possible to make the toolbars themselves more dockable? (The way they were in 2x.) Sometimes I'd like a toolbar along the side or bottom of the window.