Our plugin does not directly allow you to do text searches of individual Post Meta data. The Search & Filter Pro Text Search field uses the standard WordPress search, so looks only in the Post Title and Content. To help you control this better, on the form’s Advanced settings tab you will see 2 settings for Relevanssi.
The documentation for this is here:
https://www.designsandcode.com/documentation/search-filter-pro/3rd-party/relevanssi/
You would need to install and activate the free Relevanssi plugin as well.
Then set it up and build its index.
In the Relevanssi settings is a panel to select which categories/taxonomies to search in also.