Hello, I am looking to create a customised delivery challan - one that can be printed with a Polono Thermal printer. Is this compatible with Quickbooks? How does it work?

Welcome to QuickBooks Community, sephra-abraham-g. 

Currently, the option to edit/customised in the delivery challan is unavailable in QuickBooks Online (QBO). Any printer can work as long as it connects to the device you're using to access QuickBooks Online. Then, all you have to do is to find and open the sales receipt or any transaction you created. Once done, select the Print or Preview button and click Print. 

I also suggest checking out this article for more information about printing delivery challan in QBO: Can I print a delivery challan?

Let me know if you have any other questions. I'm always here to help. Have a happy weekend!