How to reload screenrc without restarting screen?

You could try Ctrl-a : source ~/.screenrc.

I tried the option mentioned here - Ctrl-a : source ~/.screenrc and it didn't work for me.

This is what worked for me - Ctrl-a : source $HOME/.screenrc

I have this in my .screenrc file:

bind R eval "source $HOME/.screenrc" "echo '.screenrc reloaded!'"

Which causes screen to reload the .screenrc file when Ctrl-AShift-R is pressed.

Of course, this only works if you've already got the line in your .screenrc file! To 'bootstrap' this sortcut on an existing screen session, add the line above line to your .screenrc file and then follow @Dennis Williamson's answer. After that, you'll be able to use the new keyboard shortcut.