Windows Forms Designer option missing after Rider update (Build #RD-251.25410.119)

After updating Rider to version Build #RD-251.25410.119, the "Open in Designer" option disappeared for existing Windows Forms in my projects.

Details:

• I have multiple Windows Forms projects that worked fine before the update.
• After the update, forms that were created and worked previously no longer show the "Open in Designer" option.
• When I open such a project, the Designer button appears briefly, but disappears after indexing completes.
• If I create a new Form in the same project — it does show the Designer option and works correctly.

Question:
How can I re-enable the designer for existing Forms in my project?
How can I tell Rider that these are valid Windows Forms and should open in the designer?

Thanks.