Launchers are a divisive topic in the Mac universe. Some use the built in Spotlight and never look beyond that. There’s a bunch of others, all of which I have tried, more than once, before coming back to ObDev’s LaunchBar. Its best qualities are speed, extreme configurability, and the fact that it learns your favorite shortcuts just by typing them often. I have been a happy customer since 2009.
Like other launchers, it scans your Applications folder(s) for new things every so often. What LaunchBar does not do is follow symlinks (aliases), which becomes a problem when you use
linkapps feature, which creates aliases for MacOS application bundles it installs in your Applications folder.
The simple fix for this is to open the LaunchBar Index, go to the Options for the Applications section, and add
/usr/local/Cellar to the search path.
Let LaunchBar do its rescan and QGIS will be at your fingertips, along with any other MacOS application bundles homebrew may have installed.