Such positions are sometimes created and attached to full W3 professors, essentially as a temporary Assistent in the old parlance (compare C1). Whether this is actually done may depend on your field, your Bundesland (you are in Baden-Württemberg, where this is possible in general) and even your university.
You may want to talk to your supervisor, who may have the most vested interest in having you continue on board, especially if you have a proven track record and/or specialized knowledge. However, it would probably be better for your CV to get a "normal" Juniorprofessur to show that you can stand on your own feet, rather than continue in your supervisor's working group.
Alternatively, there are ways of getting funding for a few years that may not be a Juniorprofessur in name, but in effect. For instance, the DFG's Emmy Noether Program. After a few years funded through this program, you will be considered berufbar. You will need to apply with your own research proposal.
The advantage is that this is very competitive, and if you snag one of these, it is a true mark of excellence. In addition, you will be independent of senior professors, and it offers quite a number of networking opportunities. If you can manage to get one of these, it would be ideal.