The Foundation encourages the thoughtful design of projects such that they result in multiple functionally independent, decoupled libraries. One of the ways this can be done is by using multiple GitHub repositories per project (one per decoupled library).
If you have an existing project and you'd like to add more repositories to it, you should have all permissions to be able to do it. If you'd like any advancd configuration for your repository, build or release process, please reach out to the FINOS infra team.
Although GitHub doesn't directly support the concept of a "project" (a group of related repositories), the Foundation keeps track of this information, and uses it in the catalogue, Activity Dashboards and landscape
Adding new repositories to an existing project does not require a PMC approval vote, since it's not a new contribution. Therefore the turnaround time is typically quite short (a day or two at most).