Extracted from #50392.

Sometimes the quickest way to get started with a new template or pattern design is to duplicate an existing one, and customise from there. Currently this is a manual process that involves opening the target entry, copying all blocks, then pasting them into the new one. This flow can be streamlined.

Patterns and $custom templates are relatively simple to envision, but other templates will need some design exploration to get right as the template hierarchy will need be considered and communicated during the flow.

Phase 1

• Duplicate patterns (including reusable blocks and template parts) Patterns: Add renaming, duplication, and deletion options #52270
• Duplicate $custom templates

Phase 2

• Duplicate all templates