This is an issue with the version directly from the downloaded code: I haven’t changed anything, with the exception of changing the Active SDK from 10.5 to 10.6, and that didn’t change a thing as far as I could tell.
I wanted to add a new ingredient to a recipe, and was able to create a new ingredient using the Edit Ingredients pane. I then clicked the button to add a new recipeItem to the recipe, which created a new row in the table. Clicking the combo box in the name column brought up a list of the ingredients I had created, so I selected one, but it didn’t take: the cell remained blank. I had the same issue with the Unit of Measure column.
Saving also failed, with the “Multiple validation errors” method, although if I undid the creation of the new recipeIngredient, I could.
This is the