'Play selection only' / invert-selected

Suggetion
It could be useful, if it was possible to replay only selected notes, in piano roll. Meaning that un-selected notes passed by the playhead, would be mute.
This feature would also be possible, if lmms had an 'invert-selected' feature, meaning that selected notes would turn un-selected, and un-selected would turn selected. Maby as easy as to switch a boolean(?)

The issue proposes two related piano-roll features: muting unselected notes during playback and adding an “invert-selected” action. First locate the piano-roll selection and playback entry points, then clarify whether both behaviors are required and define tests or manual checks for selection inversion and playback.

Written by the indexing model from the issue text.