Based on Abraham Mayowa Oluwasina answer provided above is the correct one. MacOS Catalina, .bash_profile is no longer apple's default shell and it won't persist your path variables instead use .zprofile instead.
In root directory,
touch .zprofile
open -e .zprofile
Add the following in file,
export ANDROID_HOME=/Users/<username>/Library/Android/sdk
export PATH=$PATH:$ANDROID_HOME/platform-tools
Save and exit
To activate
source ~/. zprofile
echo $ANDROID_HOME