I just installed the latest cpanel release (9.3.0 R5) and now the exim conf editor in whm is gone. What I have though is Change Update Preference and Update Config and both point to the same script and do the same thing. Looks like someone took out the edit conf editor and added a duplicate for Update Preferences instead!
yes, it is under service configuration but it looks like this was not thought through because there are still duplicate options for the upgrade settings and one is kind of in place where the exim editor was.