Create as many .ino's (tabs) as needed, remembering the main 1st tab must have the setup() and loop(). While this normally works, sometimes automatic function protyping has a hiccup.
When you move libraries (.h & .cpp files) remember to change the #includes:
#include <thislib.h>
becomes
#include "./thislib.h"
I have some projects with 10+ tabs. Nice side effect is you can Zip one folder and have a backup including working library code.