I'm sorry for the vague wording in this question.
I've created a login system with Tkinter but am not sure how to create a new window for the main menu of the app I want to make.
I've tried opening a new window but that still leaves the login window open and if I attempt to delete it with the .destroy command it shuts down the whole thing.
is there a way to completely refresh/open a new window?
You can call old_root.destroy() and that will close the old window. It will also reset all of the global variables in tkinter so it will be as if you just imported tkinter for the first time. So you can create a new tkinter window using tk.Tk(). I find this approach more intuitive and easier to understand/implement.
Edit: You need to first pull the data out of your entries/other widgets before you call old_root.destroy() otherwise the data will be deleted as well.
How to progress to next window in tkinter