When I add a new Label/Code (in this case "No Stop Bar") in the domain of the hosted feature layer it does not appear in the list of features that are available to add in the add feature edit option. Its appear in the table drop down list, the style option list and in the JSON code. It does not show in the Drawing info or "types" on the All layers and Tables page. There are no m values associated with the hosted feature layer. Two current work arounds: add a different feature then update that feature as the intended feature in the edit feature option i.e. create "Other" feature in Add Feature option then change to "No Stop Bar" see video below. Second option export layer to and recreate in ArcPro then rehost the layer in AGOL. Neither option is efficient or acceptable in a real world work environment. The first option works both in the AGOL and Field Maps. Screen shoots are attached.