"Add to playlist" option doesn't always "add to playlist".

Concerning the effects of the option: Advanced Settings > Performance Options > "One instance when started from file". Let's call the checked state "single instance mode" and the unchecked state "multi-instance mode".

When dealing with a selection of multiple media files, the 'play' and 'add to playlist' (abbreviated) context menu options in explorer's right-click context menu should basically have the same effect in single-instance mode, adding all selected files to a single instance's playlist. That is indeed how it behaves.

On the other hand, in multi-instance mode, they should function differently. The 'play' command should launch them all in separate instances -- and it does -- but the 'add to playlist' command should not -- and it does, which is the problem.

'add to playlist' in multi-instance mode does NOT create a playlist, and instead unexpectedly opens every media file in its own instance, just like the 'play' command. This should not occur in either single-instance mode or multi-instance mode.

The distinct behavior then for 'add to playlist' should be, when adding multiple files to a playlist, it does so in a new instance in 'multi-instance mode', and in 'single-instance mode' it keeps adding more files to the same instance's playlist, but in both cases it should be adding to a playlist, not opening every single file in the selection individually in a separate instance.

When in multi-instance mode currently there is no way to add multiple files to a playlist, since it just opens them all in separate instances.