In Notes.app, how do you add columns to a table? I'm using Version 4.5 of Notes.app

There's an option to add a table. I see that if I tab through the table then rows will be added, but I'm not finding a way to add columns to the table.

Is it possible?
Yes. Add a table and click on it and you should get something that looks like this:



Notice the two small rectangles, One on the left of row 3 and the other on top of column 2. Right-click on these small rectangles and you'll be given an option to add row or column.