Following is the function I have added in the .zshrc configuration file to create a Notes folder if it does not exist and if the folder exists it has to cd to that folder.
function mnotes(){
if [ ! -d ~/Desktop/Notes ];then
mkdir ~/Desktop/Notes
else
cd ~/Desktop/Notes
}
I have set an alias as follows:
alias notes=mnotes
After sourcing the .zshrc file. and typing the command notes, it will create the notes folder, but doesn't cd into it if the folder exists.

You forgot to add the fi to end close the statement: