I deleted a toolbar I didn't mean to delete. The dialog is not "wrong", per se, it's just that it's not fool-proof (I can prove that!), and not even nearly so. I'll explain.
I saw the checkbox checked for the toolbar I wanted to delete, so guess what happened? Yeps, the highlight bar was on another toolbar, and that is the one that got deleted. No, I didn't bother reading the popup that said if I was sure I wanted to delete ""--I just clicked-away, because the toolbar name with the checked checkbox next to it, registered in mind at the time that it was, well, the toolbar with the checked checkbox! With my color preferences (a compromise because Windows 10 does not allow users much leeway in UI element color selection), the highlight bar doesn't really stand out, so that didn't help matters.
I think the toggling of toolbars really belongs in Preferences, with some other means for toggling them temporarily while available in Customize during customization--the latter rendered in some way that cannot be misconstrued to be an indicator of the target for the action icons above the toolbars list. Perhaps all toolbars should be automatically shown during customization... the possibilities are, of course, endless.
I was able to recover the toolbar from an early backup, by restoring the backup, drag-n-dropping the toolbar icons to a folder, then restoring the latest backup and recreating the toolbar with the saved icons (.dcf files actually).
(My third day with Directory Opus--and I am spending more time learning and configuring DO than using it, but it's worth my time to do so).