That’s no problem with PhysicsEditor :
Don’t use joints for this. It’s a pure waste of cpu power. Multiple fixtures are all you need.
Each fixture can have separate physics parameters.
Use the polygon button from the top toolbar. If you have complex sprites you can also use the tracer and remove the points you don’t wany by double-clicking them. Then add a new polygon.
You can assign ids to the fixture that you can retrieve later: The corona’s collision gives you the fixture number inside the sprite. Use the getFixtureId function from the generated lua file to get the id.
You can also use sensors to detect if the sprite will collide soon.