Only recently i have discovered how to make this function which is by using a point-entity called filter_activator_name.
On all brush-entities that have the option of "Filter Name" in the list, this is what only can trigger the entity including the flags in the brush-entity.
The way to make a filtered trigger is by creating a point-entity and make it a filter_activator_name and change the Filter_Name to the name of the entities you wish to activate the trigger.
If you want multiple entities with different names to activate the trigger then put in an asterisk ( * ) to where you want the rest of the entities to pass through; such as if the Filter_Name was Prop, then anything with the name Prop* at the beginning of it's name will pass through.
Below is a small graph of what only can pass the filter if the Entities beginning of the name is Prop.
