Hi,
In the documentation, it's written that you can import .blend (from Blender) :
I tried with Blender 2.80 and 3.5, and it's not working.
I found this answer from Phil (https://answers.flexsim.com/questions/90640/blender-281-shape-not-imported.html), and I can export in .dae from Blender, so it's not a big issue.
If .blend are no more supported, I think you can remove it from the Valid 3D Object File Types List.
Thanks.