Add description of logic to design specs

Published design specs include specific design details of a screen (fonts, colours, etc.) but I can't see where to add a description of the logic in the page. E.g. if I have  two radio buttons I might want to describe the different behaviour if one is chosen over the other, or the validation to apply to a particular field.

Of course I could write a separate document that references the XD design document, but that would be more difficult to maintain.

So my questions are:

1. Is it possible to edit a design document in the free version of XD to add a description of the logic in a screen?
2. If not, is it possible to do 1 in a paid subscription using XD?
3. If neither 1 or 2, is Adobe considering adding this functionality?

Thanks!