Hi Mark-Kashman - I use this a lot *within* a site, my issue is with cross-site lists. Such as the example I mentioned.
eg, the "HR" Comms Site within Sharepoint has a list of all "Applicants" that are received. Each department has its own Comms Site, and they would like to be able to relate their own internal lists to the central "HR:Applicants" list that they have access to.
I've only been able to find documentation that needs a Windows PC to perhaps create external data types - which does not really help within a pure, browser environment. Access to MS Azure SQL or other cloud databases should be a really simple address/connection issue.
The ability to include the "Site" within the related columns would solve this quite simply.