It would be useful if you could see, from the Highlighter app (or whatever special-kind app), which clients to go to, to see the result. I had to try out four, to figure out where I could find my notes.
Like a "Supported by" label or badges.
Discussion
Like an "Open with..." feature?
Already designed that and shouldn't be hard to implement, since apps can advertise what they support with Nip-89.