To fix the warning about fs.inotify.max_user_watches the IntelliJ shows, it is necessary to set a value for the fs.inotify.max_user_watches and then apply the change.

Here are the commands necessary to fix the issue on ArchLinux:

sudo echo 'fs.inotify.max_user_watches = 524288' >>/usr/lib/sysctl.d/50-default.conf
sudo sysctl -p --system

More information about this can be found in here and in here.