Many to many relationships show up as a sub panel on both sides of the relationship. So in this instance if you go to to the details page of a contact and scroll down you should see a subpanel listing all the contact’s accounts. Similarly if you go to an account you should see a sub panel listing all the related contacts to that account
Regarding creating multiple relationships by accident this is easily done, but thankfully it’s also easily fixed. If you go back into studio and relationships if you double click on one of the extra relationships you’ve added by accident it should take you to a page where you can edit the relationship, which has a delete button at the top you can use to remove the relationship.
you actually don’t need to create an additional relationship. The existing relationship between accounts and contacts actually is a many-to-many relationship. You can enable an accounts subpanel for your contacts module by creating the following 2 files:
It will list the accounts to which the contact is linked in a subpanel below, the field “Account Name” will only display one of them. If wished, the field “account name” can be removed from the detailview and editview in studio
The proposed solution is upgrade safe (as long as no big architectural changes are made)
There is no need to add any additional many-to-many relationship, as this solution already uses the existing one delivered with the standard installation