Your LimeSurvey version: 6.17.11
Own server or LimeSurvey hosting: LimeSurvey Cloud
Survey theme/template: Default

Hello, I have enabled assessment mode in Notifications & Data settings. 
However, when I edit a List (Radio) question with Yes/No answers 
in the new visual editor, I cannot find the assessment value field 
for each answer option. Where can I find it in LimeSurvey 6?

Hi, are you using the new survey editor? (It's the default for new LimeSurvey accounts) You can't enter assessment values ​​there. You need to switch to the classic editor (by clicking the LimeSurvey icon in the top left, then clicking your profile name, and then setting "editor version" to "classic").