Might it be possible to have the 'prune played tracks: keep the last X tracks' setting which in the Now Playing Preferences, added as an action so it can be assigned a hot key and added as a toolbar button?
Usually I have it on all the time when playing music. But when I am auditioning and adding a bunch of new albums, or doing some album editing, it has to be turned off so that tracks don't disappear after playing parts of them.
It's no real problem going into preferences, but it would be nicer to have a hotkey, and it seems like it would be a quick, easy job.
I don't know how many users would find it useful, and I understand you might not want to make the actions list too long. So alternatively, a toggle option might be added to the Header Menu above the playing tracks pane instead?
Thanks for this consideration.