clearing photos from Imports file in Photos 3.0

Do you want to remove photos from Imports after you added them to an album?

Import can only be modified by deleting the photos completely from the library.

But you could use a smart albums as a work-around.

• Create a smart album with "File > New smart album".
• Then set the rule in this smart album to "Album is not any".
• Click "+" to add another rule "Date added is in the last ... days" and combine the rules with "Match All".

Now you have a new smart album, showing you only new photos that still need adding to albums.

My screenshot is from a newer system than yours, but this should also work in Photos 3.0 on High Sierra.

You don't. The Imports album is just a view of the photos that have been imported. They are only links to the original file and don't take up additional hard drive space.