Very good description of trap-emulator can be found in it's repo.
In order to make it work locally you have to make following things:
Run IDEA (and SnmpManager) as root in order to make it capable of receiving snmp traps
It is good to run following 2 commands to set the rights in the snmpmanager folder (run them inside the folder):
sudo find . -type f -exec chmod a+rw {} \;
sudo find . -type d -exec chmod a+rwx {} \;
it is better to run these 2 than just chmod -R 777 as most of the files don't need to be executable and git will show that as a change for a file (which means basically all the files)
sudo -b /Applications/IntelliJ\ IDEA.app/Contents/MacOS/idea
IDEA looks into different configuration folder as sudo, which will likely make you install the license again (also all of your “standard” settings/plugins might not work)
you will also need to reconfigure your grails path in case it has been configured relatively to your regular user home folder (which is usually the case if you use sdkman)
Configure trap emulator with your computers ip (not localhost)
Your trap-emulator command should look something like this: