R pasting character vector within emmeans

Question

I have a fairly large list of variables that I want to collapse across for estimating marginal means via emmeans. I'd like to list these out once to keep the analytic code more clean. Here's a sample:

covs_mrg <- c("male", "race4", "unemployable")

Then i'd like to just be able to refer to covs_mrg where it says nuisance = like:

mrg_mns <- emmeans(emp6mos_out, ~ tx, type='response', nuisance = c("male", "race4", "unemployable")

I've tried using the following, but emmeans doesn't seem to recognize it:

covs_mrg <- paste("c(", paste(shQuote(c("male", "race4", "unemployable") ), collapse=", "),")")

I've even tried wrapping the result within as.formula(), but that didn't seem to work either. Any help is appreciated!