cloud_tweak

This video covers the cloud_tweak rig type which lets you modify things on a bone which was created by the generation process.

This is useful for getting more specific behaviour tweaks out of the generated rigs, but using too many of these can result in a messy metarig, so they should be used sparingly.

Sidenote: Making such minor tweaks via the post-generation script is also a possibility, for those of you with Python knowledge.

You can get a written description on the wiki: cloud_tweak.