SSMS Dialog Box issue

This is a known SSMS bug, especially in versions 18.x through 21.x, that occurs when opening Views containing UNION or UNION ALL in Design mode—the visual designer fails to render the query, triggering a hidden modal dialog that locks parts of the interface. The best solution is to avoid Design mode entirely: go to Tools → Options → Designers and uncheck “Open objects in Design view”, then open views using Script View as → ALTER To → New Query Editor Window to edit them directly in T-SQL. If SSMS is already stuck, try bringing the hidden dialog to focus with Alt+Tab, or close SSMS via Task Manager. Updating to the latest version (21.6 or later) may reduce occurrences, but professionals generally avoid the View Designer for complex queries and manage views strictly through SQL scripts.