Open the "Personal Settings" window, then click the mouse in front of your nickname, press the space bar to insert one or two spaces (not too many, otherwise the nickname will not be displayed completely), and then click the "Modify" button to modify it. In this way, when the other party updates your information or logs in again, your avatar will be at the top of its list (online), and now it is impossible for the other party not to see you.
Similarly, if you want to put someone at the top of your friends list, just "rename" him and add one or two spaces before his name.