Good news, this feature is partially done. :)
Planner tasks can now be copied to other plans. To copy a task, click on the “…” menu on the task. From there, you can select a different plan to copy the task to.
Updating the status to “Try this instead” and have added the clarification that after 30 days the name is once again available.
The reason for this decision was that Channels can be restored 30 days after being deleted. During this time, we intentionally don’t support creating a channel with the same name. After the 30 days, the name is available.
You can workaround this by restoring a deleted channel, renaming it, and then deleting the channel again. The previous name is then available for use.
This workaround has already been mentioned in the comments and if an immediate reuse of a Channel Name is required, this is the recommended solution.
Thank you for your continued feedback. The feature team is currently reviewing this ask and investigating how best to accomplish this. Please continue to provide your comments and votes. We will post an update as soon as one is available.
Still under review by the feature team. Nothing new to report at this time.