I've been struggling with this myself.
Take a look here at this plug-in--works for stand alone QB or in the cloud. There are also a few videos you can watch, and you can download a free trial (last time I checked).
Another way is to go to Inuit website and download the instructions and files for their SDK, and basically create the connection yourself. This is beyond my skills, but probably easy for someone with the right know how.
I don't see a link to a plug-in.
The plug-in is FMBooks Connector from Productive Computing. The SDK referenced above outlines the protocols for communicating with QuickBooks (QB) via their API, but some kind of plug-in will be required to create and manage the connection.
FMBooks Connector for the Desktop version of QB creates an XML Request in memory and then passes it to QB. QB hands back an XML Response, which the user than parses using the plug-in's functions. The plug-in also has functions that allow a developer to write and read the XML directly, which offers a lot more functionality to those familiar with XML and XPath filtering.
FileMaker integration with QB Desktop has a learning curve that is somewhat steep for most users. Creating basic Requests and processing the Response is pretty straightforward, but there are a lot of places where Errors can occur that are poorly documented.
Integration with QuickBooks Online is possible using the FMBooks Connector Online plug-in. Basic integration processes are no more difficult than with the QB Desktop, but anything more than a basic "Query by ID" requires the developer to write a SQL query string.
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