Also, You can select one of the blocks to save to the props library, you will see a dropdown button called "Select Subset"  Click to open it and you'll see all the items in the scene listed with a tick box to the left. Check all the blocks you want to save as a single 'prop set' .

If you choose this route, it can be helpful to parent all the blocks to one so when you load them again you can move them all by moving the parent.

Hey! His nose is dry! ... Someone should lick it,  just in case. - Diego