Thanks, Nils, for taking the time to respond! I did not know about that trick with ctrl for selecting one column. Thanks a lot for sharing that with me!
I have a few more suggestions to share.
In the deck builder page, an ability to select all the cards in one section (main, side, custom section, or maybeboard), with one click. You could put a checkmark button (maybe saying beside it, something like, "select whole section") at the top of the section that does this.
In the details page, I like how you can view the price of cards in your main deck. Extending this function to sideboard would be just as useful. You have the total price listed but no option for individual cards. By the way, what source is this total price from (tcg player, card kingdom etc)? It would also be useful for users to know where the total price is from. You could simply put text beside it, or on a mouse hover over.
Also to do with prices, being able to see a list of your maybeboard with prices would be handy as well. I often keep cards in my maybeboard that I'm thinking of buying for the deck to test out, but don't have room in the main. So it would be handy to know the price, as I could easily sort out too expensive cards. One solution for this would be to have a price column (or the option to enable/disable a column) in the "Your Deck" section of the deck editing screen. Another solution would to have this information on the details screen, but you currently don't have maybeboard on this screen, so this would be more work to implement. Anyways, I prefer it on the deck editing page because it allows you to easily remove the cards that are too expensive. Also having this price column in the editing page removes the need for sideboard prices in the details page (which I was asking for in previous paragraph), so you kill two birds with one stone (side and maybe prices).
In the card editor screen, there is actually nowhere where it says the decks name. It would be easy to fit this in. The place I would put it (because it would use already empty real estate, is where it says "Your Deck (main:60/sideboard:15)". Instead of the words "your deck", could be the deck name. Or it could be right beside that as there is lots of room. Having the deck name shown helps cut out user confusion, especially when they made a copy of a deck (it's good to be reassured what deck ur working on).
Another feature that would be nice to have is the ability to make subsections within the maybeboard (just like you can in the mainboard). My maybeboard often gets large, and since there is no way to organize it, going back through it to see what cards should go into the main can be difficult and time consuming. So being able to make subsections would be really handy, and fix this problem.
On the compare decks page, it would be handy to have a directory of all your decks posted on that page. So you can easily select one of your other decks to compare with. Because right now it is a bit of a chore to have to open another tab, find and open that deck, copy its url, then paste it.
With the starting hand tool, adding even more buttons (at least 1, but 2 would be great) that either shade the card another colour or remove the card entirely (i prefer shading). This way you can simulate, and easily keep track of, multiple zones in a game of magic, and therefore make it easier to test how a deck plays out. Because currently you're only really able to keep track of cards played. And things get confusing when trying to simulate "look at the top
x cards of your deck" effects, mill effects, creatures dying, discarding cards, etc, because we currently only have two "zones" to work with (hand and one other)
Thanks, Nils, for providing this wonderful website to the community! Hoping this feedback helps!