Modify with a Prompt plugin is unable save the generated output to editor

Raised MR!589 to close the issue. Kindly review.

a.dmitriiev → made their first commit to this issue’s fork.

Thank you @annmarysruthy, I have also done some clean up, as the base class already provides some form common form fields that are not needed anymore in the plugin class if not overriden.

Looks good, thank you. Getting merged.

I tested this locally, and the code works fine.

Also being merged with 1.2.x