At this stage I believe the only option is to use Qlik's native REST API to hand encode API calls and fetch the data you need. We have done a fair amount of work on this in the past - feel free to message me if you'd like to discuss further scott@pomerolpartners.com
Something else that may be of interest to you - a Xero connector was part of the Blender.io acquisition - hopefully we'll see that pop up in the application automation section soon.
If you are using Qlik SaaS you can build an automation that uses the OAuth2 connector to connect to Xero. From there it is possible to build automation(s) that pull data from the API. We have found that works quite well.
