Rhino’s attribute user text is a really flexible feature, so much so that various objects can share keys and have different numbers of them. What I think would really help in terms of managing attribute keys and values is if you were to be able to create groups of attribute keys. The purpose of this is that you can modify the attribute group and all of the objects to which the particular attribute group applies are updated to incorporate the new attribute group and the way the attributes are organised (ordered).
Here’s a simple mockup:
But ideally, there should be no need to add numbers for sorting (there should be a dialog in which you can edit these with arrows to move up and down, drag and drop, proper separators and options to add buttons to fields and or add an expression to a value (so it can be auto computed like with text fields, but then based on user input).
For example, if I create a wall, I need there to be keys for its total height, width, start- and end height, as well as finish materials, etc. If I could create a group of attributes that I could apply to every piece of geometry that is supposed to be a wall (whether a closed polysurface or a curve whose attributes make it a wall by using Grasshopper), I could more easily add all the necessary attribute keys to new in one go.
In fact, this attribute group could also allow for ordering attributes using collapsible headers. So I may add the geometric properties of a wall under one header section, whereas I move the material attributes under another.
Moreover, it could allow me to specify whether an attribute key’s values should be a boolean button, a dropdown with a specific list of preset values, etc. That way, it could turn the user attribute text into more of a custom input UI with buttons. Just like you can add buttons to Excel spreadsheets or similar to how Revit families have various buttons within its family properties.