That sounds similar to what we do. I used to track manually in a spreadsheet all the backlog jobs awaiting shutdown. After sometimes, this list can be listed from CMMS based on the work order user status AWSD with the original job priority with quick/temporary fix done. Provided the data in CMMS is up to date.

What is combined shutdown (priority 4) in your case? Combined steam out & gas-free?

Priority 4, combined shutdown we have used for T&I turnarounds. With this priority we have planned all the jobs for the turnaround years in advance, do distinguish them from all other maintenance/engineering activity. It worked so well that we have decided to use it also for "pre-determined shutdowns" like decoking. Most of the jobs that must be done during a shutdown, and require extensive planning and scheduling, receive now priority 4