I have run into the same issue as described in this forum discussion when using VS 2022.
When trying to add a Dynamics GP Form I get
“The designer could not be shown for this file because none of the classes within it can be designed. The designer inspected the following classes in the file: DynamicsGPForm1—The base class ‘Microsoft.Dexterity.Shell.DexUIForm’ could not be loaded. Ensure the assembly has been referenced and that all projects have been built.”
This was using VS 2022. If I take the same project and load it using VS 2019 I can add the form with no issues.
Is there a way to add a Dynamics GP form using the extensions for VS 2022?