Microsoft has identified an issue affecting SharePoint Designer functionality for creating custom Forms within SharePoint Online. After careful examination, Microsoft has determined that there is no known fix for this issue and has elected to disable the custom Form creation feature effective as of 3:00 AM UTC on Saturday, April 25, 2020. This change does not impact the ability to edit previously created Forms or other existing features in SharePoint Online Designer.

After this change was made, users may have received the error: “Could not save the list changes to the server,” when creating new Forms.