A surprising number of database people and Windows users in general don’t know about Alt select. This is a Windows technique not unique to SSMS that allows a user to select an arbitrary rectangular region of text and delete it, cut it, or copy it.
Where I find Alt select particularly useful in SSMS is when I have a bunch of inline comments that are too far to the right. I want to delete much of the whitespace in front of them to move them to the left without disturbing any of the rest of the T-SQL.
In the screen capture below, you can see that a rectangular region is highlighted in light blue. I selected this rectangular region with the mouse. It can be removed by hitting the delete key, pressing Ctrl+X, or right-clicking and selecting Cut.
Before selecting the text with the mouse, hold down the Alt key. I recommend not touching the mouse at all before holding down the Alt key. After holding down the Alt key, place the mouse cursor at any of the corners of the rectangle and move the mouse to select your desired rectangular region. You can even paste the rectangular region of text that you obtained with this technique.
The Alt select technique also works in Word, but not Notepad.