The failing of the editor to edit any arrays other than text strings, text matrices and lists of text strings is so old that everyone has forgotten it
is a failing. The NumEd facility (look for the icon of a grid in the session menu) was added decades ago as a stop-gap. I haven't tried David's editor but I guess it is apparent that David did not consider (or considered it to be too hard or unnecessary) to edit items in unnamed spaces. Nor it seems has Dyalog enhanced NumEd to edit arrays in spaces. Even named ones.
'zz'⎕ns''
zz.asd←2 3⍴⍳6
⎕SE.NumEd.numed: cursor not over a valid name
An effort was made by Dyalog a few years ago to level the playing field between named (dyadic ⎕NS) and unnamed (monadic ⎕NS) spaces but they are still not the same in a number of ways and are destined never to be so.
Also Dyalog's short-lived experimental interpreter APL# (APLSharp) was designed to make all spaces unnamed and indeed non-hierarchical.
One solution to all this would be to come up with a notation for embedding higher dimensional arrays in code.
http://archive.vector.org.uk/art10501450