Re-assign VOB and Cell ID

Click on the VOB/Cell ID identifier in the PGC Editor to bring up the dialogue, where you can use the slider to assign a different existing VOB/Cell ID to the cell or create a new blank cell to replace the cell in question (leaving the current cell unreferenced if it is not re-used).  When a new blank cell has been created, it can easily be reused several times by clicking on Use last blank cell in VOB.

Note the warnings!

If you are changing the cells in a title, you may also rebuild its time maps.  This can be slow for a lengthy title.  You can safely forget about this if you plan to do further edits and rebuild the time maps later (See also Title → Rebuild Time Maps)