How can I delete global credentials ? I have it for SSH and I prefer configure different credentials for each device I have to scan (I dont have same user/password on my linux, mac and device)
You cannot delete global credentials. Simply create other credentials and assign those to your machines. If Lansweeper is successful in scanning your machines using those credentials, it does not try the global credentials.
Global credentials are "last resort" credentials. They are only tried when all other credentials of the same type fail.