Following your suggestion to open an issue to make a sugestion, here's one idea:

"Automate and improve issues transfer"

Here's a goal:

• be able to move all the issues of one repo to another (over 10K issues of the same org)
• It should not send notifications
• It should mimic the behavior of the github "transfer issue" button : create redirects, keep comments, all PR/interactions
• keep milestones, labels, assignees ...

We got a few parts here and there:

• https://docs.github.com/en/graphql/reference/mutations#transferissue
• https://docs.github.com/en/rest/reference/issues#create-an-issue
  • we can pass labels ans miletsones
• https://docs.github.com/en/github/managing-your-work-on-github/transferring-an-issue-to-another-repository
  • through the UI, magic "transfer issue" button
  • This will create a redirection from the old rep URL to new rep URL and this is a must.
• https://github.com/ahadik/git_mover
• https://gist.github.com/jonmagic/5282384165e0f86ef105
  • does not notify

But no definite solution! What would be your take on it?
Maybe this could be a nice experiment to stream about.