Connect Harlo to Excel and Power BI

Quick: one page, no code

1. Make a Harlo API key. In Harlo, open Settings, API keys, choose Create API key, name it Excel, and copy it. You'll paste it in a moment; Harlo shows it only once.
2. In Excel choose Data, Get Data, From Other Sources, From Web, then Advanced.
3. URL parts: https://harlo-api-dev.pages.dev/v1/invoices?format=csv&limit=100. Under HTTP request header parameters type Authorization on the left and Bearer hk_… on the right. Choose OK, and Anonymous if Excel asks how to connect (the key is already in the header).
4. Choose Load. Data, Refresh All updates it.

This brings the newest 100 records. For everything, use the query below.

Every record, with Power Query

1. Data, Get Data, Launch Power Query Editor. Choose Home, Manage Parameters, New Parameter: name HarloApiKey, type Text, current value your key.
2. Home, New Source, Blank Query, then Advanced Editor. Paste:
   Power Query MCopy

   let
       // Your key goes in a parameter (Home > Manage Parameters > New), named HarloApiKey.
       Resource = "invoices",
       GetPage = (cursor as nullable text) =>
           Json.Document(
               Web.Contents(
                   "https://harlo-api-dev.pages.dev/v1",
                   [
                       RelativePath = Resource,
                       Query = [limit = "100"] & (if cursor = null then [] else [cursor = cursor]),
                       Headers = [Authorization = "Bearer " & HarloApiKey]
                   ]
               )
           ),
       Pages = List.Generate(
           () => GetPage(null),
           each _ <> null,
           each if [has_more] then GetPage([next_cursor]) else null
       ),
       Records = List.Combine(List.Transform(Pages, each [data])),
       Result = Table.FromRecords(Records, null, MissingField.UseNull)
   in
       Result

   Change Resource to read loads, payments, customers or any other list.
3. Choose Done. Columns holding a record (like customer) have an expand button in their header: pick the fields you want. Then Close & Load.
4. If Excel asks for credentials for the API, choose Anonymous.

Power BI

The same query works in Power BI Desktop (Get Data, Blank Query). Because the base URL is fixed and the rest goes in RelativePath and Query, the Power BI service can refresh it on a schedule: after publishing, open the dataset's settings, set the data source credentials to Anonymous, and turn on scheduled refresh.