What is the best way to storage data with templates for procedural generator?

I am creating a generator for a level.
The structure of data for it:
The fist dimensional row’s is a list of templates.
In second list of template’s objects

When I released the structs and Data Tables I understood, that adding a new templates or editing old are too hard, because I don’t see end result. I see text, but I need a visualization.
I don’t have an idea how the other cope with this task.

Please tell me how work with this data.

Maybe I need to write a simple MapEditor for this?