Adding new design elements to the DS interface is something very difficult to do - plus, there's a big chance that Google will bring this type of feature themselves in the future.

You can make the suggestion here: https://issuetracker.google.com/savedsearches/578413

The HostPrefix feature is added to version 2018.11.02! :)

Good idea, it's an easy one to fix!

I haven't implemented the cascading Save yet, but if you press ctrl+shift+1st letter of button you now have shortcuts for every active button.

This is now supported directly by Google - see https://support.google.com/datastudio/answer/9125317 

Done in release 2018.10.25 - a new dark theme option :)

Da Vinci improves the following elements in the editor:

- highlight variables

- dark theme option

- code reformatting

Google already provides the option to enlarge the window (something that was in the old Code Editor for GTM extension)

Because of the way the interface handles this, I can't really do this with Da Vinci.

However, I would recommend you do your custom reports with Data Studio, which is much more flexible and can produce better looking reports.

Hmmm... I can see what could be done.

This is improved in release 2018.10.20 - just click on the timer icon to toggle the values. As a bonus, there's now a countdown shown beside it, so you know how much time is left before the next refresh.