Derived form is write protected

### Environment

Visual Studio 2022 - Community Edition, Version 17.5.2

### .NET version

.Net 7.0

### Did this work in a previous version of Visual Studio and/or previous .NET release?

Yes: With Visual Studio 2019 and .Net Framework 4.6.2

### Issue description

A derived form cannot be edited with VS 2022:

See attached project:

- BaseForm.cs: is the base form class
- BaseMDIChild.cs: inherits from BaseForm.cs
- BaseMDIERPDataChild.cs: inherits from BaseMDIChild.cs

This form seems to be write protected. You cannot insert any control.

### Steps to reproduce

1. Open the project, compile it
2. Open the form BaseMDIERPDataChild.cs and try inserting a control

### Diagnostics

_No response_