Before I delete the photos from recently deleted I would like to back them up

Once they are in Recently Deleted, they are essentially no longer in the Photos Library, and there's not much Photos can do with them. But you can get Info.

I just tried this: You can select them all and do ⌘-i to open an Info window that has mixed up information for all of them. Then you can type, maybe, RD (for recently deleted) into the keyword field. Then all the recently deleted pictures will have the keyword "RD," and you can do a search for that, or better, make a Smart Album with

It will say 0 items, because there are no pictures in the Library with RD as a keyword.

But, when you Recover them, they will all go back into their former albums, and they will all be visible in the RD Smart album. You can export them or whatever you like, and then delete them all. And now, they will all have 30 days, because they've only just now been deleted. And the RD album will be empty, again.

What do you think?

You have to restore the photos from Recently Deleted to be able to export and save hem.

Once you have saved them, move them back to Recently Deleted.

You are right, your precious photos are in danger there, because they will be automatically deleted after 30 days.

Before you move them out of the Recently Deleted album select all and assign a unique keyword to them with the Keyword pane (⌘+K). Then you can create a smart album with the criteria: Keyword is "xxxx" and have them all in one space where you can export them and then delete again.

Addendum: it's essential what Richard.Taylor said. Missed his post originally.