I´m working on a patch that uses nested ds-arrays with [draw array]. but events from the template for array b throw an error:

scalar: couldn't get array data for event callback

Is this something that is going to be fixed in one of the next releases?
there are some more things i noticed in the patch below.

purr-Nested-Knubs.pd

I have a comment in the code about that:

/* given symbol "x123456", search the fields of a scalar's template for
   a t_array that matches that addy. For now we only search the toplevel.
   We can probably also search arbitrarily deep by making this recursive.
   But the one person I know who uses nested ds arrays hasn't asked for
   that, so let's see if we can just make it to the end of this software's
   life before that happens. */

It appears I've underestimated the number of people willing to use nested data structure arrays in their patches.

I'm tryig to do a Gui Generator for the lv2plugin~ external with nested-ds. So in the patch i posted above, the knubs -symbol name field would be the controlparameters names, and in the toggles name field i'd like to store the plugins-recieve symbol. But to get both the parameters name and the plugin-slots-recieve symbol from the knubs draw-events I'd need nested data structures. It should be like a channel strip.
I like the idea of having a matrix of widgets and use nested data structures for sequencing, state saving etc.

I'll take a look and see if I can get it working.

In the meantime, you can add an issue to the tracker for this one:

https://git.purrdata.net/jwilkes/purr-data/issues