Inside the Aero app: Click in the filter box at the top of the Summary column. Type the word diamond. To see only templates that are NOT premium, click on the funnel icon and choose does not contain.
On the Aero Workflow website: Go to the Library page and look for the Summary column. Click on the three ellipses in the right corner of the column. Hover over the Filter section and then choose "Contains." Type the word diamond in the field below and click filter. To see only templates that are NOT premium, choose "does not contain" from the dropdown instead of "Contains."