This isn’t exactly what you are asking for, but I mention in the following post how you can have reusable custom forms. The important thing is that each form must have it’s own single row work table. Also, when navigating to that custom form, it’s important to use ‘Show Detail Screen’ instead of ‘Show New Screen’. The form layout will stick to that table when you view the existing detail screen, instead of a new screen.
I’ve even used the same custom form for adding rows as well as editing existing rows. It’s a little bit to set up, but not too bad. Whether I’m in Add mode or Edit mode, it’s still using the same custom form screen. Plus, I can open that same custom form from anywhere in my app. The only trick is that you need to establish a single relation, or Single Value → Whole Row, to that custom form work table. Do that in any other table where you need to navigate to the custom form. Then you can use the ‘Show Detail Screen’ action through the relation (single value).