Whoops, it's Enhanced Slave list. Let me find the Discord if that makes it easier.
If you list out step by step what you did to install the game, I can try to recreate the problem. As it is, I don't have the error and my lines of code do not seem to match the line numbers your files have.
All I can say as a starter right now, is that the error is complaining about "slavetabopen" not existing. This is a function inside "slave_tab.gd", which my mod does not touch at all, but Random Portraits does.
That said, most of the time the game complains about functions not being found, it is because a prior error caused a file not to fully load, and the "missing" function is part of what didn't finish loading. Are you sure there were no errors prior to the one you reported?