It appears a major UI update went live this week for the web player. For the life of me I can't find the "Add to Queue" button on the web player. You used to be able to right-click on a song and the option would display.
This is a must have for me. I often hear an artist from the discovery playlist and want to throw in a few other songs by said artist to get a feel for them without losing my queue. Right now I have to break the current queue.
Attached is what I'm seeing today.