I am a little confused because you mentioned change orders and document change requests, but then you said you only have one process. Do you mean that every document change goes through the change order process and also the document change request process?
I urge you to not have a decision tree. What will happen is that people will not look at it, and your document control person will become the bad guy telling people they are doing things wrong. It is better to build the decisions into the form. Here is my suggestion, which worked well at a previous company:
There was a change request form and a document change order. Not every change required a change request. On the document change form, this question was listed: "Is this a change to design, equipment, labeling, manufacturing process, material, software, specification, supplier? __ No __Yes, CR#__________.
If the answer was yes, the originator of the document change needed to list the change request number. The change request form had questions like, what is the verification/validation plan?, what is the affected product?, what is the proposed disposition?, which risk management documents were reviewed?, what is the proposed change to severity rating and occurrence rating?, etc. It also had an indication of whether all required actions had been completed.
If the answer on the document change order was no, the originator just continued working on the document change order.
Hope that helps.