Searching in the Customer Account Fields app is easy. Filters can be combined and you can even filter on the values of the fields you created in the app. The results table is customizable to add or remove the fields you're interested in.
The "Field" drop-down shows all fields, including your custom fields and Shopify default fields
The operator dropdown allows you to filter based on your own comparison criteria.
You may combine filters to further limit your result set.