Given:
In 2sxc 8.5:
Not sure how to do #4 in the latest version of 2sxc.
8.4 had a dropdown where entities could be changed over time
I believe you got stuck on a configuration. 2sxc 8.x has many new features which you can enable/disable on such a relationship. I believe right now you have set it to
so you have one item mapped, but you can't remove it, and you don't see the dropdown because you didn't adding more items :).
So just go to the entity-field settings and configure it.
Warning: there is a special case where you may have an old entity-field, and never configured which input-type you want (because there used to be only one). In this case, you want to first set which input-type you want to use (Entity-default), then you'll get the remaining fields to set:
and then