Before AOR you can just go back to the forms and change whatever you like that will change the checklist.
For example, in my second WE I was promoted so I entered on WE as analyst and another as a consultant, however the system then asked me for TWO letters, so I went back deleted one of then and put Analyst & Consultant in the position field and the system went back to only requesting one letter for that position.
After AOR/eAPR then if you need to change something it needs to be via CSE and I'd only recommend you do that if it's something very important.