To build several digraphs in one RStudio window, you must first create a list of dygraphs objects and then display a list of dygraphs using the htmltools package. Yihui Xie from RStudio provided the answer here: Answer Yihui Xie (but without grouping).
Here the R code works, which creates diagrams of highlighted grouped diagrams:
# load packages library(quantmod) library(dygraphs) library(htmltools)
The R code above creates the following highlighted graphical charts:

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