After clicking Add, clicking on the current value of Deck brings up the Choose Deck popup.
But in Stats, if you want to change the Deck away from deck:current, you have to manually type in some new value. Perhaps there could be a Choose Deck popup here as well?
If I understand your request correctly, the Stats screen already has this feature. However, it might be a bit hard to discover since, in my opinion, the button is positioned somewhat awkwardly.
Hmm. In all this time I never noticed that button down there.
The question then becomes: what is the reasoning behind having two redundant places to specify the deck? Would it make sense to move that button to the top? As a general rule, the bottom area is for buttons that exit the form (typically “OK”, “Cancel”, things like that) and not for buttons that configure the form itself.
You could have the deck/collection radio buttons stacked vertically. The deck radio button would have the deck selector button next to it, while collection would have the text input search field as before.
The button that opens the ‘Choose Deck’ popup was a later addition to the Stats screen. If I recall correctly, it was introduced around version 2.1.60 (edit: it was first introduced in 2.1.61, see Anki 2.1.61 - Changelog).
Also, it serves a slightly different purpose compared to the search bar at the top of the Stats screen. While this button allows you to change the current deck, the search bar can handle more complex queries, such as searching for (deck:"deck one" OR deck:"deck two") -is:suspended flag:5.
I agree that the current placement of the button feels a bit odd, and that it seems logical to move it to the top. Your idea of stacking the deck and collection radio buttons sounds good to me. Additionally, I think it might be worth considering changing the button label from “Deck” to something more descriptive, like “Current deck” or “Change current deck”.
