Hi,
Tables are a very tricky thing when it comes to editing them.
When clicked on the table, you can see basic table editor at the right (in Format panel) where you can add/remove columns, change background etc.
but there is no option for editing the width only.
So for now, my advice would be to double click the table, click on the HTML icon <> in Format panel on the right
and you will see HTML code where values for the table can be added.
and in the window "Try it yourself" paste the code and see the results.
Hope it will help at the moment.
Marija,