I would like to export the entire list of our Line Items Record ID and a custom property. I can tell there is no option to export Line Items for time being. However, I tried exporting them via Reports. But, the reports doesn't show Record ID for the line item. Also, I tried the BATCH read endpoint. But, it requires a criteria to be met in order to return some line items and I wish to get all of them no matter what.
You may want to check out this tool in marketplace, it is spreadsheet view which allows you to filter/search/export deal line items. We use it to quickly add line-item to deals, but the filter function might be helpful in your use case
It'd be great if you could also share your feedback in our HubSpot Idea Forum. We use it to collect ideas on how we can improve the product for our customers. Product pays particular attention to the top voted ideas & takes them into consideration along with other feedback channels as well as their own vision to understand what features will be most valuable. Thank you!