Did you try using the this? It shows how to create a relationship between a person and their favorite hotel. https://experienceleague.adobe.com/docs/experience-platform/xdm/tutorials/relationship-ui.html?lang=en  

It has nothing to do with AEP.  The CSV files structure does not support Arrays.  If you look in your key column, you see you have a comma in the field value.  That for a CSV file is interpreted as a field delimiter. While I recommend using a JSON file instead, if you have no other option, you need ...

Unfortunately, I haven't needed to dive into it at that level yet, so don't really know which to recommend. I put them both in one schema to see the overlap (Web SDK includes all of Mobile except for one area, which is the application object).  So my initial response is you could use them both w/o a...

I'm not sure why you would want to do that.  You may be getting into some compliance difficulty if you hold onto data in some sandboxes while the expectation of the Data Subject (i.e. your customer) is that all data is being deleted.

Here is the Mobile Field Group: AEP Mobile Lifecycle Details Tutorial: https://experienceleague.adobe.com/docs/platform-learn/implement-mobile-sdk/app-implementation/lifecycle-data.html?lang=en   You might also try looking at the Web Details Field Group for this.  Here is the link: https://experienc...

The mergePolicyId is optional and not needed if you only have the one default merge policy (which I highly recommend).

It should delete from all Sandboxes.

This is a quick work around: You can always create a new SegmentAdd your Segment (under Audiences)Click Convert to Rules (on the right side of the Audience Name)Change the new Segments Evaluation TypeSave as a new segment  

I see.  You may want try defining your segment in such a way that people fall out of the segment based on what you are trying to do with the realized state. Second, you can do what you are looking to do, but: It is a bit cumbersomeYou may run into scenarios where the underlying segment is resolved a...

@Ikmoo It is easier and better to use the Audience tab.  It helps when the segment job is running to ensure the segment membership is up to date.