Ever since Microsoft spend 9 Billion to buy Skype, they have been messing with it making it less and less user friendly.
End of Rant !
How do I change Font size in Chat window, it is ridiculously small..
Skype version 18.104.22.168 on MacBook Air HighSierra
PS here is an example of arrogant answer ..
Changing font size using the new Skype is currently not available. You will be using the default font size whenever using the new Skype version. Susan_S. Skype Community Moderator