I think you should try exporting the transition list to a different filename and/or folder on your computer.
Is there anything unusual about the folder where you are trying to export this transition list?
When you export a transition list, Skyline first writes everything to a temporary filename and then, as the last step, renames that temporary file to the filename that you had chosen.
Skyline is failing on the last step of this process: renaming the temporary file. I do not believe that the error your are seeing has anything to do with what was actually written to the transition list. For some reason, Skyline is unable to create the file with the name that you requested. I could imagine that this could be caused by a virus protection, but those sorts of failures to save are very rare.
Are there any special characters in the filename you are saving as?