Mentioning in this enhancement request that this one would be important for those people who are not allowed to setup github hooks:
In my project, we are not allowed any incoming hooks (long story, not negotiable) – so for us it is important to be able to configure a git polling interval for projects in a multi-branch configuration.
As a firm example: We do a full scan of our github projects for new projects with Jenkinsfiles twice a day, but would like to configure those jobs to start polling github for changes every 15 minutes. This would allow the full scan to occur just once a day, but the job to be configured to poll and build on any changes in those projects more frequently.
As I read and understand this, polling triggers would also be part of the configured job properties – just wanted to mention this specific use case.