Can't select quota to edit on Google cloud quota edition screen

You can't ask for quota changes while you are on a trial account. You need to activate/upgrade your account to premium. After that, make sure you have an owner role to your project as Nicholas suggested.

After that, go to the Quotas page and select a row in the table. You should be able to select the little box on the right hand side of the screen the selected quota. Then click EDIT QUOTAS on the top of the screen. It will then request a quota increase which will be sent to Google Cloud Support.