How to copy photos and preserve them after deleting from Imports

Actually, what you're asking doesn't make sense in the way that Photos works.

You don't "copy" or "move" pictures into an album. Pictures aren't exactly "in" an album. An album is just a list of pictures. As Old Toad says, an album is a playlist of your pictures. When you "put a picture into an album," its name is added to a list of pictures to display when the album is clicked. So two albums can both have the same picture name in their lists, and that picture will show up when you click either album, but there's only one picture-- it's just on multiple lists. And when you remove a picture from an album, its name remains in the lists of other albums, and the file still remains in your Library. 

So an album gives a specific view of your pictures. My Grand Canyon album, for instance, offers a view of pictures taken on various trips to the Grand Canyon, and my Trip to California album shows the pictures on that trip, some of which are the same pictures as shown in the Grand Canyon album. Both albums are each pointing to a single file stored in the Photos Library. Having a picture in 5 albums takes no more space than not putting the picture in an album at all.

The Imports View, is a special list provided by Apple whose purpose is to show all of the pictures in the entire Library in the order they were imported. You can't remove a picture from the Imports View without deleting it entirely. Likewise, the Library View is a special list provided by Apple whose purpose is to show all of the pictures in the entire Library in the order they were captured.

These special views are provided by Apple whether we want them or not. I keep all my pictures in albums that help me see the ones I want together. I only look at the Imports View or the other special views when I need to see what I did lately.

I often copy pictures from my Photos album and paste them into a text or an email. I also paste them into Word or other apps as I need them. I also copy them into other albums-- it doesn't make an extra file. There's only one file for each picture (and some thumbnails, and such.)