For feature-to-table relationships, to add/edit a related record there's no other option but to edit or create a parent feature first. Of course you have to configure the parent layer's form previously to allow this.
For feature-to-feature relationships, it works the same BUT when I click the edit icon in the Map Viewer I see options to select/create a feature both for the parent and the child layers. So I can create a new feature in the child layer directly this way and leave the foreign key field blank, thus this feature ends up unrelated to any existing features in the parent layer.
I guess this may be useful to someone somehow but I think it doesn't in general terms so my guess is that this behaviour can be configured/disabled in some way. I haven't found it so far. Does anyone knows?
