Prefs has been explained a dozen times in the last two weeks, and has been used to help clear issues for years.
It's the file Logic creates for it's preference settings. When you adjust preferences In Logic changes are made and saved to a preference file located in the computers User/Library/Preferences folder.
8. Delete user preferences
Before deleting user preferences, note any specific preference settings that you’ve made, and save any custom key commands you've created. Deleting preferences removes any custom preference settings and custom key commands.
To delete the user preferences, do the following:
- Quit Logic Pro X.
- In the Finder, choose Go > Go to Folder.
- Enter ~/Library/Preferences, then click Go. (Note: exactly as written) ~/Library/Preferences
- Remove the "com.apple.logic10.plist" file from the Preferences folder.
- If you upgraded from an earlier version of Logic Pro, also remove the "com.apple.logic.pro" file. It is also advisable to delete the com.apple.logic.pro.cs file.
- Restart your Mac.
Don't do this if you're not having problems.