Custom CSS : condionnaly changes the padding settings of a collection item

It looks like the custom CSS elment only accepts CSS properties for that element in the syntax

cssproperty: value;
cssproperty2: value2;

I’ve asked how we can select different id’s and child elements here: How to add backdrop-filter to custom CSS - #3 by benFortunato

I found this confusing as well. It would be good to have a little information button explaining how this custom CSS component works.