@Sebi — How do you feel about adding a new "foil etched" flag? Or do you have another idea about how to handle the foiling variants?
This wasn't an issue in the first iteration with Commander Legends, since WotC gave all the foil-etched variants their own collector numbers (e.g. regular/foil Sakashima was #89 whilst foil-etched Sakashima was #561). Unfortunately, this is no longer true with the advent of Mystical Archive. Whether a card is regular, foil, or foil etched, it will have the same collector number regardless.
Stores such as TCGPlayer resolve this with parenthetical descriptors at the end of card names, a practice Deckbox has thus far been able to avoid (for which I'm glad). In the past, Deckbox has resolved this by using its own made-up collector numbers,* a practice I also don't believe is good. And when Deckbox hasn't implemented some form of differentiation scheme, it creates what I'll call the Tahngarth, Talruum Hero issue, in which the version of that card that gets imported by default from a CSV is the special alt-art foil of that card instead of the regular one. Because the card name, edition, and collector number all match, Deckbox has a hard time differentiating. This also notably occurs with the basic lands from BFZ — during CSV import, some default to fullart, some default to non-fullart.
Since the prices on foil-etched vs regular foil may be wildly different, it'll be important that these variants can be differentiated and properly linked to accurate pricing sources. And I predict these examples will only become more and more prevalent as WotC continues to push flashy variants. May as well get ahead of the game now!
_____________________
* At least in original Zendikar, in which the non-fullart basics were given collector numbers 250-269, even though the printed card simply appended "a" to the fullart variant's collector number, e.g. Plains #230 and Plains #230a.