It would be very useful if I could filter items on Fab and/or in the launcher based on which engine versions are supported.
You can. Click the filter button->compatibility->choose engine version range.
Thank you for your reply, but the filter button in the launcher only filters by category not engine version. If there is a filter button on fab it is well hidden. Could you possibly include a screenshot to show what button you are talking about?
FAB means the marketplace where you can buy assets. There is an engine version filter.
However, you probably mean your library of already bought assets. There is no engine version filter. Library enhancements are currently in development according to the roadmap. Nonetheless, many assets can still work on another engine version.