I seem to recall that this mode was quite easy to use in previous versions of BIAB. I never did use it much but, as I recall, when a note was selected by the mouse it turned red and I was able to move it up and down the staff using the up-down keys. When the delete button was pressed then the note disappeared and the remaining notes were modified to complete the correct note length for the measure. Now this might actually be in my imagination because I have worked with lots of applications like Muse and Sonar that have similar score features, but I know it was not difficult to change a score.

I have just tried this in 2020. Selecting a note in Mono mode mode for the melody does not give me any visual indication that the note has been selected. However, moving the note up and down with the mouse does work, but not by using the up down keys.

If anybody can tell me this was the behaviour before 2020 then I will be satisfied.