Hello, Luke. Currently, the Custom Field feature cannot request or store unique GPS coordinates. The GPS data is linked to the Timesheet, whereas Custom Fields are meant for additional information or notes.
Since the customer-level GPS is too broad for you, we can set up each site as a Sub-job or Project as an alternative. To do this, navigate to the main customer, click on the plus sign next to their name, type in the name of the Sub-job, specify the site, and then click Save.
This way, when a team member clocks into a specific Sub-job, such as Site A, the GPS coordinates recorded during that clock-in will be associated with that particular project in your reports.
Let me know if you need anything else or have any other QuickBooks-related questions.