HI Niels,. I got frustrated waiting for this so I built one myself. Presenting FetchXml DetailsList. donschia/FetchXmlDetailsList (github.com). This Custom (PCF) Control that takes a FetchXml query and column list and produces a read only subgrid for Model Driven apps. Not sure if you are still needing something like this, but if so I hope this helps you.
HI Niels,. I got frustrated waiting for this so I built one myself. Presenting FetchXml DetailsList. donschia/FetchXmlDetailsList (github.com). This Custom (PCF) Control that takes a FetchXml query and column list and produces a read only subgrid for Model Driven apps. Not sure if you are still needing something like this, but if so I hope this helps you.