Yes, you can hide or unpublish an auction item at any point before, during, or after the auction!

From your dashboard, manage your selected auction, then click on Items.

Find the item you wish to hide or unpublish and click on the 'eye' icon on the item's top right-hand corner.

This will hide or unpublish the item from your auction.

To undo this, simply click on the 'eye' icon again.