We used to use this functionality in the legacy version(AX) of Dynamics when there was new distribution job being added. I am not sure if this is relevant, if you are not using (N-1) in D365.
Based on the data distribution definition (an XML file where you can define relationship between different tables ), the "Generate query" button will generate the X++ queries that will be used to define what all relevant data needs to be send to the channel DB. For example, even if you have 1000 products in your released products, only products in your assortments gets pushed in channel DB. This is actually taken care by Retail Data distribution definition.
You can refer my blog below, to understand how you can add additional filters to definition.
blog.shafeeque.in/.../
