I know XSplit has an option to automatically split recorded videos at a user-defined file size, but is there an option or hotkey or something that will let me make that split whenever I choose?

Right now the only solution I have is to stop the stream and then restart it again to force the break in video, which is not ideal for viewership.

Due diligence again, in case anyone googles this and finds this thread.

I talked to XSplit support directly and they said there is not a feature for this in their software, they only offer automatic splits by duration or file size. :(

Sorry I didn't catch this thread the first time round. I personally use VideoReDo to cut up video pieces. I use it to compile a segmented video of my best segments.