I was trying to edit multiple tracks. Specifically, I wanted to remove many (~400) tracks from a playlist.

My default muscle memory behavior is to click something to select it, then shift-click the point where I want the selection to reach to (i.e. the last track). But clicking always played that single track.

Somehow I realized that you need to shift-click the first track of the batch and then you can shift-click down to the end of a group to highlight them all. You can also Ctrl-click to select a group of individual tracks that aren't in order in the playlist but again you must ctrl-click first.

Then you can perform batch editing easily, whether by dragging the group of tracks to playlists or right-clicking to apply options.

This might have already been obvious to many users but was driving me crazy until I just realized it.