Yes, in fact one need not even bring Collada into the workflow. Unity does a nice job of importing SketchUp files directly (I’m using the most recent Long Term Support version of Unity, which is 2018.4, so you have to store your SketchUp files in 2018 .skp format, but that’s no problem). Once imported, Unity’s FBX Exporter seems to handle conversion just fine. The only problem I’ve noticed is that SketchUp and Unity work well together when instancing meshes, but Unity’s FBX Exporter creates a unique copy of every mesh.
That is, if your model includes, say, two identical knobs and you represent them with SketchUp components, when you import your model into Unity, Unity only uses one mesh that each of the two knobs shares with the other. That’s exactly what you want, as it is efficient and guarantees that any changes to the shared mesh will affect all models that use it.
However, Unity’s FBX Exporter creates a separate copy of each mesh. The result is that the exported model will have two meshes defined, one for each knob, even though it could have used just one mesh.
That, of course, is purely Unity’s problem, not Trimble/SketchUp’s. But, it means that if I want to make a final model in Unity’s own internal format (they call it a “prefab,” and their Asset Store criteria also require that you provide one), you have to choose between creating it from the inefficient FBX version with redundant meshes in it, or else extract one copy of the redundant meshes and replace all references to the others with that. Further, to avoid leaving the (now unused) redundant meshes in the FBX model, you have to export each component separately. It all works, in the end, but it’s just a major pain the rump.
All of that, of course, is purely my problem.
Thanks for the pointer to the DAE/FBX converter. I will give that workflow a try. Maybe it will produce FBX files without redundant meshes. If so, that might be a solution I can use.