Hi James,
As far as I am aware, there are no changes in SketchUp 2020 that adversely affect CabWriter 3 and its models. I have been a 2020 beta tester since the beginning of beta testing and have found no issues. They did change the name of Layers to Tags, but it is a name change only (perpetrated on SketchUp users just to confuse them). We are working on CabWriter 4 at the moment, and I don’t see any issues there either (so far). There is however, one issue that Mac users should be aware of with regards to SketchUp 2020; the latest Catalina operating system has some issues with 2020. Most of them can be resolved by re-installing SketchUp after upgrading to Catalina.