I've trying add custom class to trumbowyg-button-group.
Yes I know it's easy to add though btnsDef using class: attribute to a button. But I need to add to the button group not to the button.

Any help would be appreciable.
No option allows that.
What are trying to do?
Umm, I'm actually trying to remove some margin of a ::before inside a trumbowyg-button-group which contains a specific button which has class: trumbowyg-link-button.
Have a look, I'm modifying the style of the buttons:

I want to remove the margin this ::before:

Yes, I've tried to write some css to achieve that, like this:
.trumbowyg-button-group > button.trumbowyg-link-button {
&:before {
content: none !important;
}
}
But as far I understand, it is not possible to select parent of pseudo element. So, I think there is the only way to achieve this by putting a custom class on this specific button group.
Use :nth-child :)
Most helpful comment
Use
:nth-child:)