I appreciate your concerns Terry and I guess I must start by saying as much as I like notepad++, I don't like how their instances work. This issue shouldn't change any behaviour (from a user's perspective) other than not being able to open the same file twice.

The idea is that each group (what we pretend is an instance) will be almost completely self-contained. Each instance will have its own shell (they will not share, etc.) and the windowed design will remain (for now...).

What they will share is the main tkinter root (Tk instance) and the bottom layer of a stack-like file-list system (which I failed to properly describe in the original message). Calls will only descend the stack as far as necessary, but it allows one group to bring another group's editor to the front when the file tries to open a second time (like how an instance can raise any of its editors).

The finer details are yet to be confirmed as I don't have any code, but it is likely that settings will take effect immediately across all groups and I have yet to decide whether the 'window' menu should be unified of per-group.

I understand that the immediate benefits of this issue are not worth the change required, however I believe it would be highly beneficial going forward for groups to be able to communicate (like my previous example of creating a tabbed interface).