Nested Wildcards and Combinatorial Generation

[DrJimmyBrungus]

I've run in to a problem that I hope I can get some hlep with. A simplified version of what I am trying to do:

prompts/PositivePrompt1.txt
prompt, prompt, prompt, by __artist__

prompts/PositivePrompt2.txt
prompt, prompt, prompt, by __artist__

prompts/PositivePrompt3.txt
prompt, prompt, prompt, by __artist__

artist.txt
ArtistName1
ArtistName2
ArtistName3
...
ArtistName50

Using combinatorial generation, I would like to generate every possible prompt, (i.e. go through every PositivePrompt## file), but not use every possible artist. I just want the prompt to pick a random artist from artist.txt when it is called in PositivePrompt.

Using __prompts/*__ in my main prompt, it go through each prompt file like I want, but will also go through each possible artist for each prompt file.

I tried changing the PositivePrompt files to instead read: {1$$__artist__} in an attempt to only pick one artist, but this did not work.