As a user, I would like to make an independent copy/clone of an existing plan in Jira Software Data Center. This was implemented in Jira Cloud already as mentioned in Don’t recreate your plan, duplicate it, but not in Data Center.

This would allow:

• Rapid exploration of proposed changes to a schedule, without loss of the original schedule.
• Rapid preparation of several candidate schedules with different prioritizations.

The Scenarios in Advanced Roadmaps can help with part of those use-cases, but scenarios do not allow changing plan settings, as those would reflect in all scenarios.

The user interface could be a "Copy" operation added to the items in Portfolio>Manage Plans, similar to the copy operations elsewhere in JIRA.