if you wanted to have some premade widgets that you just toggle on/off you can make them as separate widgets and add dynamically to another widget blueprint. This way you can design them in design view but still only load them when needed. You might want to read about “Named slot” a bit for that, comes in handy.
Not sure what you mean exactly. You can use create widget node and create base classes of widgets (like button, horizontal box, etc) and then set all the parameters in blueprint.
it’s just, that sounds like pure hell to me. Usually I think you’d prefer to use the designer to make them, and just set parameter values through code.