Apologies for not seeing your response sooner Vlad
There's three viable approaches. Once they've searched for "generate a password" or any such trigger phrase, the "password generator" widget shows... In which there's either a dropdown similar to how 1Password does it
Or a "toggle" (checkbox with some styling) which toggles between "normal" and "readable" or something along those lines
Lastly would be my favorite approach - Styled radios.
Here's some examples to how others have done this:
https://1password.com/password-generator/
https://www.nexcess.net/web-tools/secure-password-generator
https://www.lastpass.com/features/password-generator
https://xkpasswd.net/s