Your comments

We don't plan such possibility. It is an element of our current business model. 
Vertabelo supports only crow's foot notation at the moment. Maybe we add others notation in the future, but it is not on our road map now. I leave the question opened, to allow other users vote for it.

There is no n:m relationships because of Vertabelo operates at the physical level, in which such type of relationship doesn't exists. At the physical level n:m relationship is decomposed into two relationships (n:1, 1:m) and a join table. We are planning some microfeatures that can simplify creating such decomposition. 
It is fixed and on the production.
We analyzed this a few months ago and decided not to do. The main problem is related to foreign key naming convention. Every database architect may have own naming convention, so it hard to follow it. 
Thanks for your suggestions. We rethink how to do it better.
It works as described in yours suggestion. When nullable is checked and you check the PK the nullable field is unchecked automatically. 

Did you encounter situation that both nullable and PK were checked at the same time?

We''ve just fixed it. It will be on production with the nearest upgrade - I mean next week.

Thanks.
We would like to keep Vertabelo UI for basic elements simple, so we don't plan to extend it in such cases. 

But you can add such index to the model using table "Additional SQL scripts" tab as you can see on picture below.