Hi Richard,
Clearly I am on the same page as you with this! I had already realised it was connected with the "family groups" of fonts but didn't want to make my question over complicated. But you have confirmed that this is not a fault with my own PC and is the same for everybody.
I had also worked out that "Regular" fonts usually show up but (as you say) not Segoe UI - the very one I want! You are also right about using Segoe UI Emoji. Increasing the size and adding bold makes it close to the default Segoe UI Black.
This is a rediculous bug for a commercial piece of software to have carried for so long. What makes it more frustrating is that the full fonts list is available in the 3d editor so somebody at Pinnacle must know how to do this right.
Still, I have hundreds of other fonts to choose from. Like my mother always told me, "Never mind Peter, there's plenty more fish in the sea". And that's why I ended up married to Helvetica-Normal instead of Segoe UI !!!!