If these are the three dots I’m thinking of, they should only be seen for the currently-selected track and for one that your pointer is hovering over (at least that’s what I’m seeing in macOS 10.15, Catalina).
Clicking it brings up the track’s context menu:
This is the same context menu you get if you right-click or ctrl-click the track. It’s also very similar to the Song menu on the menu bar, removing disabled items and adding a few items from other parts of the UI:
I’m not sure why it the three-dots UI element is present, since there are two other ways to bring up the same menu. Maybe Apple decided that this was one case of a hide-and-seek interface that they didn’t like and made a visual indicator for the context menu.
I don’t know of any way to turn it off.