I managed to write a script to build a xstack command, that was great. I recently tried to build a command to automatically add a silent audio track on inputs,

I managed to write a script to build a xstack command, that was great. I recently tried to build a command to automatically add a silent audio track on inputs, while also adding pause and concatenate 300 small videos, all of this in a single command, but I still have a lot of trouble understanding how stream selector work.