The best source of information for creating custom location rule is, like I said, to look at the ones that are built into ACF. These can be found in
/wp-content/plugins/advanced-custom-fields-pro/core/location.php
All of the custom locations rules I’ve eve built have started by copying some portion of the code from one of the existing location rules or by using these as examples to build my own code.
You can make the location rules dynamic by checking for the values in other arguments that are passed to your location match rule. You can see all the values that are passed to your rule starting on line 1237 of the file I mentioned.
