I came across this forum:
Altium import workflow, then delved into it. Harnesses are really just a way (AFAIK) to connect signals between sheets. The method I came up with was to use a bash shell to just add a hierarchical label, a wire, and a global label in the ‘harness’ sheet. You can grep the signal name from one of the sheets that contains the harness sheet, then do a quick hook up. If anyone wants the script, I’ll be glad to post it.