I don't know if this functionnality already exist but we would like to manage jobs, credentials, folders and users and maybe more with Rest API.
I found documentation explaining how we can create or run jobs but I didn't find anything for managing users and credentials.
If it is not possible, I purpose to develop a plugin wich will integrate all primary plugins to administrate Jenkins (folder, credentials, matrix security ...).
This plugin will expose API to interract with Jenkins and theses plugins.
Please let us know if you are interrested or if a solution already exists.