This is now possible for the file tabs bar, file tree view, and other special UltraEdit "toolbars"/panes, but not for the normal toolbars with the icons on them. This might be new to v12.10b (it's the first time I've noticed it).
From the help file:
Locking the File Tabs
In UltraEdit a right click in empty space by the open file tabs will cause a tip Undockable to appear. If this item is checked, the open file tabs may be dragged from their default docked position to a floating dialog. Double-clicking on the title bar of this dialog will return the file tabs to their default docked position. If Undockable is NOT checked, the file tabs are "locked" and may not be removed from their default docked position.
Locking the open file tabs and the file tree view could be available since v12.10. It's definitively also possible in v12.10a. I don't have v12.10 anymore and in v12.00a it is not available.
The setting Undockable for the file tree view and the open file tabs is stored in uedit32.ini with following entries:
[UndockableWindows]
File View=0
Open Files=0
Looks like the IDM developers have forgotten to mention this new feature in the history log in readme.txt.
Thanks scallanh!
Best regards from an UC/UE/UES for Windows user from Austria