I don't know a good way to explain this, but let's try.
Imagine that these icons...
...are all Google Chrome, but three different profiles. That is what I want.
What happens, whether creating .desktop files by hand or using kmenuedit is this:
- the launcher will respect the unique icons I choose
- I can force Chrome not to group the icons
- The panel icons still all show the default Chrome icon...
...instead of using the icon I chose for each instance.
The reason, for the interested, is that I want to have a work profile, a non-profit profile and a personal profile which all open and can be pinned with a unique icon.
I've gotten far enough that having separate menu entries with unique icons and individual .desktop files and ungrouped panel icons seems like progress, but Plasma seems to treat any instance that points at the final binary as "the same."
Yes it's a KWin Wayland issue, and I already replied with this solution to @ja2 's comment. You should also change
StartupWMClassto name; so that the icon applies correctly.