Ok thx for the reply @PeteSharp, I was hoping we could set it ourselves in the class editor in the tab display, but seems the only option for the moment is like you reply… I’m just starting to use Blocs and trying to see what is possible. Great app so far! I was reading about the bootstrap earlier to better understand how blocs works… There’s a lot to read 
You could create that table though. Add all the classes to either a .css files and link it or put them in the page header and use div brics. It’s possible.
I wonder how this will change with Bootstrap 5?