The Problem

Some GCode-generators can't create tabs, so I decided to include them in the drawing.

The Solution

Select the path you want to add tabs to:
Change the stroke to the width of your milling bit and add little something. Example: 3.0mm milling bit → stroke 3.1mm:
Path → Stroke to Path
Choose the Node toolso you see the shape of the stroke is now a closed path):
Add nodes where you want tabs:
Remove infill and set a stroke (otherwise you can't see the deletion of the segment):
Select one newly made node and the neighbouring node and split path there by deleting the segment in between:
Repeat for the other new node:
Close the gaps in the path:
Repeat for the other new node: