Last month I was trying to get output from a struct element without external mouse objects. I now tried a different tack spurred by @jona @ingox @Whale-av and @liamg.
This abstraction acts more like 64 discrete sliders rather than a plot and doesn't need any externals.
The advantage is
Multiple instances do not cause the closing delay and errors
The slider acts like slider not a plot
There is no internal array, but the input/output can be addressed to and from an external array
Uses only the click and change output of the struct
The hotspot area at the top of the slider is duplicated in the background part, giving a larger click area
The message help is in the abstraction
Instead of using a plot array, I am now creating 64 scalars with an id and using the id as the index when clicked and the drag from y1 for the value, therefore no mouse object required
The disadvantage is
No jump on click
No plot flow
Not yet scalable (mammoth task I think)