Is your feature request related to a problem? Please describe.
I think Gutenberg is a great improvement.
But there is inconsistency to how links are managed.

Try to explain:

• text link

1. Can I add rel nofollow? No, must edit manually
2. Can I add a css class? No, must edit html

• button link

1. Can I add rel nofollow? Yes in sidebar, manually
2. Can I add a css class? Yes in sidebar

• image link

1. Can I add rel nofollow? Yes, must do manually
2. Can I add a css class? Yes, must do manually

The button link selection is completely out of sync with the rest of interface.

This is very frustrating, and also more frustrating is to explain more and more to clients how to do things.

Describe the solution you'd like
Provide an univoque interface with link selection. Allow

Describe alternatives you've considered
Going back to old editor