I hope to be at your level some day Dave, well done!
Long, I’m not OP so I’m only able to share my interpretation of what they – and therefore myself – am looking to accomplish.
Let’s say I have two CPTs (Ingredients and Recipes) and a relationship between them.
Now I’d like to use Frontend Submission to create a form that creates a new Recipe. After I write 10k words retelling the history of ever even thinking of this recipe, I want to select ingredients that go into it.
If I don’t have some rare new ingredient that I’ve never entered before, I understand from your most recent comment that this is not possible (feature request!). However, if I want to add an Ingredient to my Recipe that’s already in the system, is there a way to do so via a Frontend Submission form?