It would then be updated with the new main snapshot version.

For now, it has been set in a post-release job but its real place should be at release branch creation and thus the update of the snapshot version on main.

We already have a job updating the version on main: https://github.com/kiegroup/optaplanner/blob/main/.ci/jenkins/Jenkinsfile.setup-branch

This could be set in that job and should run only if the job is ran on the main branch. An example of such a condition can be found here