When copy-pasting the content from the new theme files I had to make sure I didn't copy-paste the section headings [PlankDrawingTheme], [PlankDrawingDockTheme] and [PlankDrawingTheme], otherwise an overwrite would be triggered upon saving.
When copy-pasting the content from the new theme files I had to make sure I didn't copy-paste the section headings [PlankDrawingTh eme], [PlankDrawingDo ckTheme] and [PlankDrawingTh eme], otherwise an overwrite would be triggered upon saving.