I use CAD software to build models for games. This is neither normal nor a recommended method, and it isn't a great method, but it is what I do and I like it.

So here is how to use transfer modes from Shapr3D to Unity via the royalty free glTF standard.

Build models in Shapr3D

Scale

I suggest using Meters as your scale, and then basically build everything to an aproximately realistic scale.
I typically use the "Minecraft scale" that a person is "about 2 meters tall".

Textures

• Shapr3D allows applying shaders to models, and this method will allow basic colors ("albedo") to be transferred into the game engine. So go ahead and use colors, but don't get carried away with "textures" like metallic, etc. as they won't transfer.
  

Export STEP file

• Use the Export feature, and chose STEP format
• The default settings are fine and will include all relevant data that can be transferred
  

Use FreeCAD to convert STEP to glTF

This can also be done with Blender, but I find FreeCAD quicker and easier if I don't intend to make any edits.

Install FreeCAD

https://www.freecad.org/downloads.php
You can either use the installer, or you can download the portable version and just stick it in a folder.
I find using the portable version best for using for conversions, since I don't need an entire installed app with updates or plugins.

• Note that if you download the portable version, it will be a 7zip file. You must download 7zip to extract it. Windows might pretend that it can extract it, but it will fail and claim the file is corrupt.

Run FreeCad

• freecad.exe is in the bin folder if you are using the portal version
• Open the STEP file

Select the model inside FreeCAD

The export function exports what is selected, not the entire file.
Do not use Select All as this will usually produce a mess, instead:

• Press Shift+b to enter "Select Mode"
• Select the entire model in FreeCAD
  

Export

• Press Ctrl+e to export
• Set the Save as type as glTF (*.gltf *.glb)
• Name the file with a .glb extension, NOT .gltf
  By using the .glb extension, which is the "binary" format of glTF, all parts of the mode will be in one file, otherwise you end up with multiple files and it is hard to work with.
  

Bring glTF into Unity

Install Unity glTFast Package

https://docs.unity3d.com/Packages/com.unity.cloud.gltfast@6.0/manual/index.html
Unity doesn't have built in glTF support, but this plugin appears to be official.

• WIndow->Package Manager
• Use the + sign dropdown and pick "Add package by name..."
  • 
• Paste in com.unity.cloud.gltfast and click Add

Drag the .glb File into Unity Project

Open up your Unity editor and Find the file in Windows Explorer and drag the .glb file into the Unity project folder where you want it to be.

Drag the imported model into the Unity Scene

Open the Scene that you want to put the model into, and drag the model from the folder into the scene

Colliders

Each side of the model will have its own mesh instance.
To add static colliders select ALL of the "roots" by click on the top one and holding Shift while clicking on the last one
Be sure to select the "root" along with all of the children.
What looks like the root will just be one of the sides, so if you skip it, one side will not have a collider.
Add a Mesh Collider to the selected entries
Now is a good time to also drag any scripts that these meshes need onto the group