So, I had accidentally closed the Toolbox Dock and went into Single Window mode. I then went to
Window > Recently Closed Docks and reopened the Toolbox Dock. This resulted in the Toolbox Dock to appear separately from the single window. From there I left the Single Window mode and it joined the two Docks together and I can no longer separate them.
As the Toolbox doesn't have a tab associated with it, I can't close all of the the tabs on the right. I guess could close the each separate tab on the left side recreate the Dock manually, but that is a lot of tabs and is really annoying. I could even reset the UI to defaults through
Edit > Preferences > Interface > Window Management > Reset Saved Window Positions to Default Values, but this seems a bit overkill. Is there a way to separate these two halves from each other in some other way?
Using GIMP 2.10.8.