I know you can split a stereo track into two mono tracks but can you combine two mono tracks back to one stereo track? Other than recording a new stereo audio track?
Lots of ways. Drop both tracks into Audacity or Reaper and export as a stereo file.
When I record on my Zoom R24, I end up with 8 mono tracks. Dump them into Reaper and mix down to a single stereo track. If you then import that into anything else, it will come in as stereo.
Same scenario, different program. Import them into ProTools and export as a stereo file.
Or download Audacity, combine them, and then uninstall Audacity if you don't want to keep it. I only had the free versions of Protools and Cubase, but as I recall, they operated in a similar manner for basic functions like that.
I think you can simply select the clips and drag them into a new stereo track. And I think Control+drag will keep them from moving in time, but I go too long without using PT to remember for sure.