To use block text selection in SQL Server Management Studio (SSMS) Query Editor Window, press and hold the Alt keyboard key and use the mouse to select block of text, or use Shift+Alt+Arrow keys to make the selection.
Block selection can be useful for editing and formatting multiple rows of code.
Here is an example what would the selection look like:
Now you can edit the whole selection. For example you can delete the whole text block. If you type 'OR', it will replace the 'AND' operator in all selected rows:
To insert text into multiple lines, press and hold the Alt keyboard key and use the mouse to select rows, or use Shift+Alt+'Down Arrow' keys:
...and just type or paste text that you want to insert into multiple lines.