I found that on Mate 20.0. lightDM GTK+ Greeter is a highly configurable login screen reminiscent of the classic GDM configuration. I have a configure this following path
usr/share/lightdm/lightdm.conf.d/60-lightdm-gtk-greeter.conf and edit this file
[SeatDefaults]
greeter-session=lightdm-gtk-greeter
and also configure /usr/share/lightdm/lightdm.conf.d/50-myconfig.conf
[SeatDefaults]
greeter-hide-users=false
greeter-show-manual-login=true
allow-guest=false
successfully configure this both file and restart the computer. Unfortunately I am failure. Because login screen could not show another login screen
Thank you
Md Iqbal Hossain