Tell us what you are trying to do?
I have a CPT with a "recommended price" and an "actual price". How do I build a view (in classic mode) that will show me all products with an actual price that is greater than the recommended price?
I've tried using a URL_PARAM but it's not working.
The way the filters work you test the post value of some field compared to a static value (even if you grab the static value from a url parameter, or a shortcode attribute).
For example, show all posts with a price field greater than 99 (whether you explicitly provided the value 99, or 99 came from a url parameter or shortcode attribute).
But you are aiming to compare the value of one field with the dynamic value of another field, and WordPress queries don't work like that. (See examples at https://developer.wordpress.org/reference/classes/wp_query/#custom-field-post-meta-parameters; you can use a variable for the value you want to compare, but it is still a static value that doesn't change once you invoke the query.)
You could do this by directly writing your own SQL queries, but you wouldn't be using Views for that.
However, all is not lost!
Without such a filter the View is going to return all posts of your CPT.
But you don't have to output them all.
That's where conditional shortcodes come in. Where you output the desired content, wrap that in a wpv-conditional shortcode that tests whether the actual price is greater than the recommended price (both field values coming from the current post in the loop).
(Note, pagination won't work as expected if you do this, as the pagination is based on the number of posts returned by the query, not by the number output on the screen.)
