I'm on a macbook pro and lost access to 2015 version overnight. I'm suddenly now in 2020 without any of my plugins, settings, shortcuts, effects. Any way to import them?
There used to be an easy method of doing this which simply involved picking up the Preferences folder and dropping it on the Audition Desktop icon. I'm prett sure that this doesn't work any more, but it was quite good - it just picked up everything that you'd stored that was additional to the 'vanilla' version and incorporated it. I have a feeling that this was pre-.xml files though. In the present version, it's possible to export the ApplicationSettings.xml file easily from the Export menu, and substituting the default version with an old one might work - but it probably won't contain everything you want. There are a couple of other files in the Preferences folder as well that you could try to substitute - like EffectPresets.xml and Favorites.xml but as I said, there are no absolute guarantees that this will work; it all depends on what, if anything, was changed about the structure of these files between versions, and whether anything new was added.
If the original preferences file was on the same machine as you're reinstalling on, then yes, Audition will attempt, during the installation, to include anything it finds from previous installations. At least that's what it's supposed to do - it doesn't always work, especially if you are reinstalling with a different user login.