I made a homebrew variant of the aberrant mind sorcerer so that I can swap out some of the psionic spells for other enchantment/divination spells, as the feature allows you to do. This worked for the most part, I modified the command already in the subclass feature so that it gives different spells but for some reason Evard's Black tentacles refuses to be exchanged for another spell. I exchanged it for Raulothim's psychic lance, and when I save the change and look at the homebrew, it shows Raulothim's instead of Evard's, but then when I apply the subclass to a character, Evard's black tentacles show up on my spell list instead of Raulothims's psychic lance. I tried so many things to fix this, copying the character, reloading, reapplying the homebrew modification, but I'm out of options.

How exactly did you edit the subclass? Did you remember to hit the main [SAVE CHANGES] button under Basic Information after you edited the subclass? If you follow the instructions in this video it may help:

At one point in this video he mentions a way to swap the spells but he used a different method than I did so I tried his and it worked. Thank you so much for your help!

Happy to help.