Today I created
I has one content-type that holds all available field types for dexterity as described in https://training.plone.org/5/mastering-plone/dexterity_reference.html
I used it to test all fields in the new barceloneta for Plone 6 (https://github.com/plone/Products.CMFPlone/issues/3061).
I even created a branch that works with Volto where not all fields are implemented: https://github.com/collective/example.contenttype/tree/volto
I think it could be usefull