I’ve never seen this before and a colleague came across this brilliant shortcut by accident.
Here’s how it works (in Notes 8 and 9 anyway):
1. Create a table in Notes (or use an existing table)
2. Hold the shift key and hover the mouse pointer over a row line (not the top one)
3. The cursor will change to a thick black line with a little blue diamond above it
4. Double click while still holding down shift
5. A new row appears !!!
This also works for columns as well. I think it’s great but that might be just me.