Profile: David Gimenez

Problem: I would like to use my checkboxes group field as filters in a custom search, but the field does not appear in the popup where I select a field for creating custom search filters.

Solution: In the custom field settings for this checkboxes group, be sure "Save 0 to the database" is not checked. This option does not work with custom search Views. If you had this option checked previously and wish to change it, you must resave any posts where no checkboxes were checked. Otherwise, you may receive false positives in search results.

Relevant Documentation:
https://toolset.com/errata/checkboxes-that-save-0-are-interpreted-as-checked-by-views/
https://toolset.com/documentation/customizing-sites-using-php/functions/#checkboxes