To directly answer the question you asked:
"No, unless you already know javascript, dojo, dijit, and the ESRI javascript api very well. If you already know those items well, then yes, if you also have an editable service set up in esri web server and portal."
HOWEVER, such a task is completely unnecessary (except for the part about "an editable service set up in esri web server and portal").
Create a web appbuilder application and add the editable service to the map. Then add the Edit widget and configure it to allow your users to edit that service. Piece of cake and zero programming required!
It is a table. When I try to publish the table as an editable service I am not given the option.
Sorry, I missed that. (And you were very clear about it , too!)
I've seen some code in the widgets about "editing related tables" but each of our gis tables are stand-alone so I've never figured out exactly what that code does.
You could certainly create a custom service in C# (or whatever) that would interact with whatever database you're using. Javascript, Dojo and Dijit would certainly work to build a data entry screen with and could be used to call your services.
Sorry not to be as much help as I thought I was being!
Thanks!
I was hoping the functionality would exist within the WAB, for portability when building different applications. For now I will consider this functionality as something custom, so maybe with a 10.5.1 portal I can create a custom widget to do this task, and bring it in that way.