I see. I not really sure if this commands wills till going to work with the latest version of Skype but you can give it a try.
Type /setrole <username> Admin in the message field. Replace "<username>" with the new admin's Skype username.
You can also use /setrole <username> Master to change a member's role to admin. The two commands are the same.
If you want to change a chat admin's role to member, use the /setrole <username> Member.
For more information, you can visit
https://www.wikihow.com/Make-Someone-an-Admin-o...
"Please be reminded that the link above is from a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it".
Let me know if this works for you.