I cannot edit or clear data from a field, because it is a part of a relationship.
Do I have have to delete the relationship, edit the data and recreate the relationship or is there another possible way to manipulate data from those fields?
thank you for your question. At this moment it is not possible to edit data which are used for the relationship definition (using Instant JChem) without deleting and recreating the relationship. The only possibility is to temporarily disable the foreign key constraint using a SQL client, edit the data and enable the constraint.