How to create such an action: IF some elements are hidden sth sth happens

Hi DW,
It's not totally clear wht you are trying to do here.
If you have the elements on a page and you want to hide them either from page load or at a certain event you just use an action to hide them.
This could then also do something else as a part of the same action.
Simple example is to make an object or put a button on the page.
Make an action>
#onclick
#display : hide named object(s)

You can add another action after this.

Nick