In case you want to use the RCon feature on your RUST server, you will have to create a new command line.
To do so follow the steps below:
From your game panel, go to the "Commandline Manager"
Click on the 2nd tab "Custom Commandlines" and then click "New".
You should now see a few options and checkboxes. If you are not sure what to type on them, fill the information below, and only adjust the "+rcon.password" field:
Click "Save" and after that, click on the "Select" button:
After you select the command line, restart the server, and the new RCon password will be set on your server.