where is tinymce config file?

Hello
referring to another post/problem I got : emails with long body text are not picked up - đź’¬ General Discussion - SuiteCRM

I think I might have found the solution with TinyMCE “Advanced Editing Behaviors” with the br_in_pre value
from

I really believe that this could solve my issue but could not find the place to put the setting in…

any thoughts?

Thank you
Serge