We use the Job DSL plug-in and store our configuration in a VCS.
When we change it there, the jobs automatically get updated in the Jenkins environment.
We also use the Job Config History plug-in, so we can easily see what has changed in a job and when a change occured.

Currently after the jobs have been updated, we simply trigger all the jobs so we can ensure that the jobs that are changed still works.
However, the more jobs we add, the more of an overhead this creates.
If I add or change a pipeline (== multiple jobs grouped with a multijob, in our case) for a specific product, I would like Jenkins only to build the pipeline that was changed.

Therefor, I would like to see a build step provided by the Job Config History plug-in.
As arguments it would accept:

• Maximum age (only trigger jobs that where changed in the last X minutes or perhaps even, only trigger jobs that were changed after the current job started)
• Queue highest parent (whether you want each individual job to be started, or want to queue the job that is at the top of the hierarchy).

Note that the second option does not necessarily mean that the "top level" job has to be changed, but if any of its children (or grand-children, ...) are changed, it may be queued.

PS: If there is another way to get the date and time a job was last changed (and by that I mean actually changed, not the same configuration saved again), I would love to know this too.
I might as well create a separate plug-in for this build step in that case.