How do you change a custom-set-variable? I went into my .spacemacs files and I see the variable I want to change but there is a comment that says to not change it by hand. So how do I do it? I did it once. But forgot completely.

customize-variable, customize (with the UI), or setting stuff on the user section of your .spacemacs (what I prefer, with setq and friends)

So if I do the customize-variable --> cider-lein-parameters I can change the variable but if I restart Spacemacs the variable goes back to the previous version and friends.

It's been a while since I've done that... The customize UI should persist if you ask it to, though

Now I mostly put them on the SPC f e d file and , e e them in place to play with settings without reloading everything.