From the Field Maps resources: https://doc.arcgis.com/en/field-maps/faq/requirements.htm
"Feature-to-table relationships, feature-to-feature relationships, and table-to-table relationships (where the first table is accessed through a feature) are supported in Field Maps. For each, one-to-one and one-to-many relationships are supported. Relationships can be up to three levels deep. It is recommended that you use Global IDs when defining relationships. User-maintained relationships are not recommended."
The following case is described in the ArcGIS Pro Resources (https://pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/create-relationship-class.ht...😞
"Simple or peer-to-peer relationships involve two or more objects in the database that exist independently of each other. For example, in a railroad network, you might have railroad crossings that have one or more related signal lamps. However, a railroad crossing can exist without a signal lamp, and signal lamps exist on the railroad network where there are no railroad crossings. Simple relationships can have one-to-one, one-to-many, or many-to-many cardinality."
If I use a crossroad:signal lamp = 1:M cardinality Field Maps won't let me set points for independent signal lamps (the feature layer doesn't show up in the menu). How do I make this case with independent feature classes happen in Field Maps?
This doc https://doc.arcgis.com/en/field-maps/faq/requirements.htm mentions 1:1 and 1:many relationships but not many:many.
I don't think many:many is implemented. I've tried as well and it never worked for me.
Yeah sorry Caitlin i'm not sure - I've never actually tried using a M-M relationship in AGOL.
Have you tried accessing your related records using an Arcade expression on the pop-up? i.e. https://community.esri.com/t5/arcgis-online-blog/show-related-data-or-tables-in-pop-ups-with-arcade/...
Again, I haven't actually done this with a M:M before, but it should be possible.
Hi Duncan and Andrea,
I believe Andrea is correct that it's not currently supported. I thought about going the route of using Arcade in the pop-up to show related records, but without the M:N support of a 3rd table housing the related unique IDs, it can't find which records are the related ones.
It is disappointing it's not supported at this time, but hopefully it will be soon!
Thank you both for your time and advice,
Have a great day!