(WeBuilder Version 15.0.0.199 - portable configuration)
Hey there,
first of all, the ! with the replacement "!important" can't be found in the AutoReplace Window in the settings menu (a search and sort function of the AutoReplace List would be really nice).
When I manually add the exclamation mark with another replacement, it automatically resets it to "!important" after I click "OK".
The ! -> !important replacement also can't be removed entirely.
This issue was present in WeBuilder 2016 as well but currently it's especially annoying since I have to create many static sites this month.
Here is a video showing the issue in action: https://www.youtube.com/watch?v=K5oH0eOO1tY
~ Daniel