how to use filter row by regexp

First thing, you should probably choose a different administrative theme for your site. What you're using now looks bad, and makes things harder to use. For example, here is how it might look if you used the default Claro administrative theme instead:

I think you agree that is easier to read that what you are using.

To answer your question directly, the regular expression should be entered in the "Parameter" textfield below the selection. Note that any selections like "Filter rows (by regexp) *" that have an asterisk like that need a parameter entered.

The regular expression can either have a leading / and trailing /, or those can be omitted - it will work either way.

The regular expression operates on the raw value of the field (not the formatted value).

You can use a website like https://regex101.com/ to develop and test your regular expressions.

Automatically closed - issue fixed for 2 weeks with no activity.