I was able to get this to work thanks to the help above. First, I bind all lists into one long dataframe (they have the same columns). Then,I grouped by the group (CNN) and did the stats.

library(dplyr)
library(tidyverse)
 
BindSUB <- bind_rows(mylist)

BindSUB %>%
  group_by(CNNgroup) %>%
   summarise(value_mean = mean(CS, na.rm = TRUE), 
           lower_bound = quantile(CS, c(.025), na.rm = TRUE),
           upper_bound = quantile(CS, .975),na.rm = TRUE)