Saving changes is not permitted error message in SSMS

To change the Prevent saving changes that require the table re-creation option, follow these steps:

1. Open SQL Server Management Studio.

2. On the Tools menu, click Options.

3. In the navigation pane of the Options window, click Designers.

4. Select or clear the Prevent saving changes that require the table re-creation check box, and then click OK.

More info from Microsoft https://docs.microsoft.com/en-us/troubleshoot/sql/ssms/error-when-you-save-table