How do I write class methods in other tabs?

I am creating an image processing methid but it’s becoming too long for me to keep track of everything. Is it possible for me to write the class methods in other tabs?

Yes.

Internally the tabs are just stitched together so
you can easily add a tab and write a class there

Just to clarify, the entire class must be in one tab. You cannot split a user defined class over several tabs.