Allow typing in the answer box in the previewer too

Let’s say I am creating a JS script similar to the following one where typing text into the answer box produces a visual change.

How to have instant type:answer feedback? - Card Design - Anki Forums (

If I want to test it, I have to first save the notetype and then open the reviewer. Things would be easier if I could type in the answer box in the template previewer itself.

Similarly, let’s say that the appearance of the screen depends on the card content. For example, a notetype where the answer box appears in some cards and doesn’t appear in others (all with same template).
To test this, I have to either open the template previewer from different cards in the browser or open the reviewer and rate the cards to get a “preview” of the other cards.
This situation can be made better by showing the answer box and allowing typing into it in the card previewer (which you open from the browser).

It is worth mentioning that AnkiDroid has both of the above requested features.