Here's how you can solve your problem: Make as many tickets as you can think of, it doesn't really matter if they contain the essence of the problem or not, it just matters that there are many tickets associated with the task. Once you have your tickets, estimate them with as much padding as possible. If the manager complains that you're padding a ticket too much, make two tickets and split the estimate.

Once you have a big pile of tickets and estimates, you've bought yourself enough time to do the work. Go do the work, then mark all the tickets as complete. You'll figure out the edge cases as you go, as long as you've made enough tickets and time to do the job at a reasonable pace.

If you have extra time left over, get started on the next thing, improve your tooling, or try to help someone else with their tasks. If you don't have extra time left over, make more tickets next time.