Co-wives and mistresses

What would be the best way to indicate rank in the case of co-wives (or husbands). I could imagine somehow adding start-end dates to each union. Or another possibility would be to create several types of unions, so that you have senior wife and junior wives, of however they’re distinguished per culture/language.

Also, it would be nice to have some sort of symbolic representation of the end of a union, say like the slash that goes through dead individuals. Would this need to be defined as yet another sub-type of union? Of could the presence of an end date to a union (if that can be added) automatically put such a slash on the union symbol.

Related to all this, is yet another type of relationship - what about extramarital unions. I think it would be the same process as adding a jr. / sr. wife.

I would suggest creating an event profile in the component registry and add to that the fields that you require. To do this I would search for an existing kinship profile and modify it to your needs then save it under a new name. Then you can create an event with this profile for each marriage and add relations of type other to each individual in the marriage and enter the required dates or rank etc… These event entities can then have symbols associated with them that will be shown on the diagram.
If the event profile has a start and end date, you can associate the strike though symbol to this data. This is the same method used to show the deceased symbol for individuals.
Extramarital unions could be recorded with the event profile above, however this might be redundant if a child was produced as the descendant lines will indicate the union adequately.