Click on the pencil icon to access the Button Settings (on the button, that you want to filter with). You can also use images, or any other element to trigger the filtering. It doesn’t have to be a button module.
Go to Advanced → CSS Class. Here you add the
Additionally, add any category that you want to filter with that button like that: efc-[your category] e.g.
Buttons have to be in a separate section, than your filterable elements. Or you add the ef-buttons class to your button row (Premium features).
Click on blue icon to access the Section Settings.
Go to Advanced → CSS Class. Here you add the ef-area and the ef-elements class.
Click on the edit element icon to access the element settings.
Go to Advanced → CSS Class.
Here you add all the efc-[your category] class you want, e.g. your efc-cats class.
Do that for all elements you want to make filterable.