Using Form Builder I want to add an individual and an organisation and so the individual would have the relationship 'contact for' the organisation. I can't see a way of doing that - is it possible?
Yes. Create a form and add an Individual, an Organization and a Relationship.
On the Relationship tab, use the Values section:
- click 'Add value' and select 'Contact A'
- click in the search box and choose 'Individual1' in the pop-up
- click 'Add value' and select 'Contact B'
- click in the search box and choose 'Organization1' in the pop-up
- click 'Add value' and select 'Relationship Type'
- in the pop-up, select 'Key contact of'
This works on https://dmaster.demo.civicrm.org (5.56.alpha1) but may not on older versions.
== Edit ==
If your version supports relationships they should show on the pop-up when you hit '+' as here: