Budget Rejection

You have two ways to set up workflow that Anaplan currently has enabled, which I think can help your question especially in respect to cost centers:

1. System driven workflow: This will allow you to establish workflow along any list - which will show up on the workflow tab next to model map (as an admin). If you have selective access assigned along the same list (top level on composite hierarchies) then you should be able to have the email address associated with that user available to use in the mail to function. https://help.anaplan.com/anapedia/Content/Modeling/Manage_Models/Workflow.html?_ga=2.167810977.1259662637.1533049470-1144842599.1518466360

2. Model workflow: You can develop an approval system for submitting budget workflows through modules set to different permission levels based on the roles that are approving. This is generally done through setting up a system of interdependent boolean line items to flag submissions, approvals, rejections, and the connection between each. For this system - in the module you establish as the submission module - you can add in the email address of the user, or use the User system list, to manage the responsible party. This would allow the approval role to use the hyperlink to open an email in their platform and draft to the responsible user - but wouldn't be templated.

All this being said, there are product roadmap enhancements to workflow that you should check on the community. Let me know if this helps.