You could convert it to a list like in the example bellow, altough I see no practical purpouse on this, could you explain why you wan to do this?
library(gapminder)
library(tidyverse)
as_list <- gapminder %>%
group_split(country) %>%
set_names(unique(gapminder$country))
as_list$Angola$year
#> [1] 1952 1957 1962 1967 1972 1977 1982 1987 1992 1997 2002 2007
Created on 2019-12-10 by the reprex package (v0.3.0)