Please Add 'Copy' Function to Buckets

You are not missing it — there is no copy-bucket option in Planner right now, and I can see why that is frustrating when the same set of tasks comes up again and again.

The closest options that do exist are at task level and at plan level. You can copy a task from its ... menu, which lets you copy it to the same plan or another one, but that is one task at a time, so it is no good for a whole bucket. The other way round it is to copy the whole plan instead — open the plan, use the ... menu at the top and choose Copy plan, which brings the buckets and tasks across with it. Then you can delete the buckets you do not need in the copy, or move the copied tasks into your existing plan. It is clumsy for what you want, I know, but it is the only built-in way to get a whole bucket's worth of tasks duplicated in one go.

For a bucket you reuse a lot, saving the plan as a template is worth a look too, so you start from that structure each time instead of rebuilding it. And the feedback idea you linked is still the right place to keep the pressure on for a proper copy-bucket button — this thread is a good example of why people keep asking for it.