Hi @CHASEONHO,
Your observations are absolutely correct. Promotion process can be can be configured with the help of preference.
However there is no such configuration setting for change request (as far as I validate it on 10.2 M030).
However if you wish to change default (OOTB) change request process, you can do it through lifecycle template.
To do this, you can follow below approach:
1. Identify which lifecycle template is being used for Change Request.
2. You can do this via Object Initiation Rule Administration at Org or Site (or even at Context) level.
3. Once you identify Lifecycle template, you can go to Lifecycle Template Administration, locate and edit the lifecycle template.
4. In this, under Workflow tab, you can change/point to new workflow you wish to use for Change Request.
5. Save and Check in modified lifecycle teamplate
6. Initiate new Change Request.
Note: As always do this testing on test server first.
Best Regards,
Shirish