from forum discussion https://en.smath.com/forum/yaf_postsm63957_Beta--SMath-Studio-0-99-7542--25-August-2020.aspx#post63957
[quote=Andrey Ivashov;63965]
There is one issue with the plug-in: invalidation of the region is not requested after menu item usage (it must be done by plug-in) so borders will be visually switched only after region redrawn, f.e. after scrolling or focus in/out.
Best regards.[/quote]
This also seems to be the cause for delayed re-draw after editing operation (you have to get focus off the image to see the changes). Very valuable hint!