Web Inspector does allow you to create new CSS rules, though it's not intuitive at all.
When editing an existing rule you can add a new rule on the same line.Once you hit enter Web Inspector will put the new rule on a new line.
If there is no existing rule for an element you can cheat one in by adding 1 pixel padding via the metrics panel, which creates in inline padding style. The edit that rules or and add new rules as above.
Again, not as good as Firebug, but might be useful for some.
When editing an existing rule you can add a new rule on the same line.Once you hit enter Web Inspector will put the new rule on a new line.
If there is no existing rule for an element you can cheat one in by adding 1 pixel padding via the metrics panel, which creates in inline padding style. The edit that rules or and add new rules as above.
Again, not as good as Firebug, but might be useful for some.
It looks like this is being actively worked on: https://bugs.webkit.org/show_bug.cgi?id=18224
I agree the lack of DOM editing UI is a problem.