Partial CodeMirror Selection with External ProseMirror Selection

Not really. The browser doesn’t allow its selection to start in editable content and end in uneditable content (or another separate editable element). It might be possible to fake the entire selection in cases like this, if you throw enough code at it, but that’s out of scope for core ProseMirror.

I think that’s already implemented by the node view’s setSelection method (when ProseMirror syncs it selection, it’ll end up calling that).