My company is trying to filter and search users by a custom field type that has their ID from another system. We are looking to do this so we can easily pull these customers up in the customer directory by searching that custom text field (their ID from the other system) and then creating a transaction/order for them. I have searched and cannot find any ability to do this through the site or the ipad app, so I am wondering if this is in the works to filter the directory by a text field or if there is another way I need to approach this. I am aware that you can do the custom query through the customers-api, but was hoping to use something already built into the square site/app.
If your setting the custom field as either a reference_id or a custom_attribute it’s searchable with SearchCustomers. 
Thanks for giving solution. It is simple but difficult.