Step 1: right click an empty mcp tab
Step 2: set select command to cast..
Step 3: First Parameter: ALL
Step 4: Second Parameter: Singular Focus
Step 5: Give it a name
Step 6: Apply
There you go.
Also if you want to cancel singular focus
Step 1: right click an empty mcp tab
Step 2: set select command to Cancel_maintained
Step 3: only parameter: singular focus
Step 4: give it a name
Step 5: Apply