A list of builtin commands for bash (list taken from man-page for bash 4.4)

bash-builtins.txt

// here is similar list for fish-shell - https://fishshell.com/docs/2.2/commands.html
source
alias
bg
bind
break
builtin
caller
cd
command
compgen
complete
compopt
continue
declare
typeset
dirs
disown
echo
enable
eval
exec
exit
export
fc
fg
getopts
hash
help
history
jobs
kill
let
local
logout
mapfile
readarray
popd
prinf
pushd
pwd
read
readonly
return
set
shift
shopt
suspend
test
times
trap
type
ulimit
umask
unalias
unset
wait
------------------------------
for
select
case
if
while
until
function