Is there some way to create a toroid (donut-shaped) object in Unity?
There is no built-in torus, but you can make one extremely easily in any modelling application, such as the free blender.
Yes but one can not alter the inner radius alternatively named as the radius of the swept circle nor the segment count which lets one create washers for bolt and nut assemblies.
The dynamic would be only for the editor as creating huge polygon count meshes would be feasible in runtime.
I see the distinction of ‘not in runtime’ causes a lot of Uniters to run away or avoid the issue.
But in the editor is where this would be perfect. Tweak the parms then prefab the object.
Archimatix lets you do this dynamically and is not destructive but you need a license. Umodeler does this but is destructive.
Probuilder is the answer.