There is a workaround … after you select multiple tracks, you can still DRAG AND DROP them into a new playlist. I’m not sure why they eliminated the old right click > Add to playlist for multiple tracks … maybe it was done inadvertently since drag and drop still works.

Right-click "Add to" and "Remove from this" playlist not working when selecting multiple songs

“As we could also reproduce this behavior, we've passed the info of the issue on to the relevant team so they can take a further look, but we can't say exactly if or when this will be fixed.”