I'm sorry for earlier answer, Snofru is right I was answering for MMW instead of MMA.

Here is the MMA answer. When you have now playing list open you can LONG TAP on One track and then you can even select multiple tracks before you add them to Playlist from The menu on the bottom.

You want the three dot button in the lower right - there's an Add to Playlist entry in that menu. Also Find More From..., Properties, Delete, and Share.

I think the answer from Peke was about MMW but the question was about MMA. No idea how to right click in Android ...

Unfortunately I cannot answer the original question.

There is two ways to do that.
1. right click on Track in Now playing -> Send To -> Playlists
2. It is possible to make shortcut to 1. by Right Click on Toolbar -> Configure and under OTHER in the right panel you have Send to playlist that you just add to any toolbar (or create new if you want) and then select track and press shortcut button.

MMA doesn't seem to have an option to add the now playing track to a playlist.... or am I missing something?

I want to random play my library and ad hoc add songs I like to various playlists.