Inserting markdown between two html tags

</div>

and be able to define specific css for tables ? Or do I have to write tables in HTML?

A how to is documented in Wrapping markdown into html.

And applying a style to your table is straightforward since the markdown is converted into HTML. Using your 'custom' CSS class you can style that table like:

.custom table {
  background-color: #fcc;
}

I've used the Classifier plugin to style specific tables and elements as well. I'll have to try @bleutzinn's link.

I actually missed how useful this plugin is :) Nice work @perlkonig