It is not currently possible to do this automatically BUT there will be a feature of "shared containers" in the near future which will allow this.

Please help us better understand your needs for this feature:

• How many blogs do you need to configure the same?
• Will they all use the same skin?

-15 blogs
-all the same skin

It's not about the skin, anyway. I have a Free html widget in the sidebar 2 container. I would like to solve, that I should have to edit only once, not 15x.

Yes, one widget spread over 15 collections will be possible in the near future. In the meantime you still have to copy/paste.