Annotate to end on edit.

[jyjokokk]

Is your feature request related to a problem? Please describe.
I've noticed often coming across the issue of how editing notes or tasks functions basically as an overwrite. When wanting to add or edit something small, you have to copy the content first, then paste it again on the edit, and then adding the new bit.

Describe the solution you'd like
I think it would be useful if it'd possible to pass a flag on the edit, which would make the edit an annotation at the end, or by implementing support for external editors.

Additional context
Might give this a go myself actually, timetables permitting.