It is certainly possible to book multiple shows using Side Door, or to fill in gaps on your tour using the platform.
There are a couple of ways to do this:
As an Artist, you can log in to Side Door, navigate to the Connect page, and search by region to see Hosts that are seeking Artists, responding to any that might meet your date and location requirements
Create your own Show Calls outlining your exact needs (location, date or date range, description) that hosts can see, review, and respond to. All Hosts in the selected regions will receive an email announcing Show Calls in their area.