Thanks for the jumpstart @ThinhDinh
I came up with a solution for the changelog (not yet for locking the edit button, which requires a timeout with math and date columns). Feel free to copy this app.
It relies on a “temp” sheet, in which every user gets two rows, once signed up (“add rows” during sign-up is not implemented yet).
Every sheet, for which changes should be tracked, needs to have two looked-up arrays and two many-to-one relations to these two above mentioned “user-specific” rows in “temp”.
Every “open edit screen” action sets the first “user-specific” row in “temp”. Every “on submit” action sets the second “user-specific” row. The comparison between those two rows is made through single value, ITE and template columns in the “temp” sheet. “Set column actions” work through the above mentioned relations.
You can monitor as many columns as you like (I implemented 4: A, B, C, D). Best is to have different columns per data type (not implemented yet).
This solution with 2 user-specific rows in temp is not sensitive to cancelled edit screens, since the first row will always be overwritten once an edit screen is opened.
Let me know what you think. Improvements/feedback are welcome!