You are right that pabot is the way to do this unless you want to hack robot internals, you just have to find a way to have it run outside maven.
I would do this by configuring Jenkins to preserve the artifacts from the maven build and then trigger another job that runs pabot against those artifacts. Another benefit of this approach is that you can easily re-run the tests on the same build without re-triggering the build. If you create your pabot job as parameterized then you could have a selection of builds to test against.
Parallel testing is tricky and you need to be very careful to keep it realistic to your products use cases especially if your motivation here is reducing test run time.
Source link https://sqa.stackexchange.com/questions/30601/how-to-run-tests-in-parallel-using-robot-framework-maven-plugin