This seems to work. At least for a simple keywordtest.
Rightklick your KeywordTest oldtest you wish to duplicate and SaveAS newtest.
Your test is now copied but the images are gone. In Explorer ./KeywordTests/Visualizer/newtest you only see newtest.tcKDT.tcVIS and no images.
Now look in ./KeywordTests/Visualizer/oldtest. Copy all files to ./KeywordTests/Visualizer/newtest
Now delete newtest.tcKDT.tcVIS (first copy the name...) and rename oldtest.tcKDT.tcVIS to newtest.tcKDT.tcVIS
Look in Testcomplete and you'll see your images are back at newtest.
Now you can Rightklick KeywordTests and use Add/Existing Item to get your oldtest back.
I tested this procedure with some small tests (I don't have any large ones jet) and it seemes to work.
Regards
Ronald