How do we remove a file from a sketch?

I have taken a large program and split it into smaller chunks. I did not make a library, I simply moved the code into another .pde file in the same directory.

I then used the 'add file' menu item to add the file which now shows up as a tab. Everything is fine. BUT... how do you later remove it? If I exit and re-enter, the tab reappears. Does it create a make file somewhere? I see DELETE (actually deletes the file) but I do not see how I could remove the tab without deleting the file.

Is there a way to remove/close a tab without deleting a file?