Just as a warning for any curious people wanting to try out CODE 6.4.10:
This version seems to introduce a major performance regression at least when opening and closing Calc sheets, which renders it practically unusable at least for me.
While trying to create a test case for the aforementioned bug, I encountered a few additional problems including changes I made that didn’t get saved and were silently lost… I also reported those findings on GitHub.
For now, I reverted to the previous version of CODE which I were using.
The performance issue I reported above as #2745 seems to be related to comments in Calc sheets / cells.