I have no idea what you mean by that.
There are blank spaces in the .exe, but it's just padding sections to align on certain widths. This padding is certainly usable and I do use it frequently.
Another thing I do is simply re-write the functionality by hand in ASM in such a way that it's more efficient and takes up less space, giving room for increased functionality.
Or I just delete something I don't care about like a boss or entity. I'll never use them all, and something like 3/4 of the code segment is entity AI.