Hmm. I checked my software archives, and was sure I kept a copy of the 13.0 installer for archival purposes, but it wasn't there. Man, I thought I was half-joking, but I guess I really did scrub the release out of existence here. That's not like me, so I must have been
very ticked off by it. Sorry.
However, from what I recall, the 3D features in 13.0 were nothing remarkable. IMO, if you need to mix 3D animation with Moho, it's better to use a dedicated 3D animation program and bring your Moho animated elements into it. It's easier, and it will look better.
Traditionally, I would simply import my Moho image sequence, map it to a polygonal
card, and place the card in the scene. This is a basic workflow, but it works great in many situations.
Nowadays, if the 3D program supports it, I'm likely to try Moho's new glTF format. Unlike an image sequence, glTF brings in the animated rig, which is useful when the rig needs to
physically interact with the 3D environment, lighting, and effects.
I tested a couple of 3D programs with Moho's glTF. The current Blender supports it. LightWave 2026, added glTF support earlier this year, but it didn't work with Moho files at the time (it didn't recognize Moho bones and made a mess with the animation). I was in touch with the LW developers about this issue, but got sidetracked...will check in this week. Moho's legacy FBX sort of works in LightWave, but it has different issues. I don't have Maya, so I haven't tried glTF there.
When glTF is not workable, using a Moho image sequence on a card is still a good option. It's what I used at DWA and in my own productions.
Either way, they're both basically result in 2D animations in a 3D environment. For interaction with an image sequence, you'll need to track the 2D image, and attach 3D items to the tracking data; with glTF, you simply attach the items to the bones.
Compositing is another option, and probably the most common choice because all compositing programs support a 3D environment, and I can import 2D/3D media and auxiliary data from almost anywhere. Fusion and After Effects are my usual go-tos, and Nuke when the client requires it.
Hope this helps.