Within the KM Editor, under the Help menu is Open Preferences folder (which opens ~/Library/Application Support/Keyboard Maestro). In that folder is the file Keyboard Maestro Variables.plist.
As usual, make sure Keyboard Maestro and Keyboard Maestro Engine are not running on the target Mac.
Also, there isn’t a guarantee that the files will be up to date on the source Mac if you don’t quit Keyboard Maestro and Keyboard Maestro Engine there as well before copying the file. Some files will, some wont, it depends on the files.