Your comments

I'm not sure I can explain it properly as I didn't completely understand what happened.
I realized that the gameobjects's materials using the shader had an incorrect path (something with "Hidden/..." instead of "Shader Forge/Flowmap"). I'm not sure why it changed to Hidden path nor why upon setting the path back to the proper path I finally was able to open it in Shader Forge. Why would a gameobject using the shader matter to the shader? not sure. I just don't know what happened ;)

Thanks for answering. Ok, so if I was doing a big "if" chain in shader forge based on "Toggle" inputs (that can be exposed as properties), it's a bad idea right? I just don't understand why that would slow the shader down since it will skip over the code, it's not gonna run the code that's in the unused if's right?