After some time learning a little bit more about R internals, S3 and S4 objects, and quantmod package, I've come up with the solution. It can be used to change anything in the graph.
A) If the legend belongs to a secundary indicator window:
- Do not print the chartSeries (type option plot = FALSE) and get the returned "chob" object.
- In one of the slots of the "chob" object there is a "chobTA" object with 2 params related to legend. Set them to NULL.
- Finally, call the hidden function chartSeries.chob
In my case:
#get the chob object
my.chob <- chartSeries(dataset,
type = "candlesticks",
main = "",
show.grid = FALSE,
name = "My_Indicator_Name",
layout = NULL, # bypass internal layout
up.col = "blue",
dn.col = "red",
TA = c(newMyTA(),
addVo()
),
plot = FALSE, # do not plot, just get the chob
#plot = TRUE,
theme = chartTheme("wsj")
)
#if the legend is in a secundary window, and represents
#an indicator created with newTA(), this will work:
my.chob@passed.args$TA[[1]]@params$legend <- NULL
my.chob@passed.args$TA[[1]]@params$legend.name <- NULL
quantmod:::chartSeries.chob(my.chob)
B) In any other case, it is possible to modify "chartSeries.chob", "chartTA", "chartBBands", etc and then call chartSeries.chob
In my case:
fixInNamespace("chartSeries.chob", ns = "quantmod")
quantmod:::chartSeries.chob(my.chob)
It is just enough with adding "#" at the beginning of the lines related to legend().
That's it.