There is currently no way to specify the origin and destination of an app highlight. _addAppHighlight assumes originatedInApp: true, newGroup: false, and is not configurable.
Created attachment 430509 [details]
Committed r278430 (238454@main): <https://commits.webkit.org/238454@main>
All reviewed patches have been landed. Closing bug and clearing flags on attachment 430509 [details].