i think defining grid (and arc) interface conventions is a useful exercise, with some exceptions, depending on the goals.
i doubt that it’s feasible to try and follow these conventions for all apps. simply because the restrictions imposed by grid itself tend to make UI much more app specific. a lot of times unique controls are needed both to fit it into 128 LEDs/buttons and to make it intuitive (as a side note, designing a friendly user interface can take more time and planning than writing the actual code).
so, designing with some preselected set of controls is doable but will be probably limiting in practical terms. it might sound contradictory considering the many very different things that were already created with a limited set of grid ops, but grid ops were built with a very specific goal in mind, to allow creating flexible enough UI within limited scripting space that teletype provides. as such they have to pack as much functionality as possible in as few ops as possible. so, say, the fader control is both limited (it works in a set way and can’t be styled much) and flexible (to be efficient for both coarse and fine adjustments). so the approach to designing grid ops was: try to limit the number of controls and their properties, but provide some other ways to style UI (like drawing on top of other controls).
if we talk about norns specifically though, i think it makes total sense to have a library of typical controls. this will help with building apps quickly, especially since it’ll be more natural to define a grid “button” and work with that, instead of writing code for processing grid presses / maintaining button state / rendering. having a predefined set of controls will also help with usability aspect, but again, i think for simple apps that’s fine but for more complex apps they will likely have a very app specific non traditional UI.
as several people mentioned, this really comes down to having documentation. so if there is some way that that could be simplified too i’m all for it! (when documenting orca i did it in power point because it’s surprisingly easy to use for diagrams, but still it’s a very manual process, i’d love some editor that would simplify that).
and having a catalog of different UI elements/approaches for grid would be a cool thing to get ideas for norns/tt/max etc grid apps!