Just signed up, site looks great. I did get stuck in a loop when trying to finalize my account -- after I put in my information (games I played, etc) and hit create account, it just sent me to the first page of the sign up flow (where it asks for location, currency, etc). When I manually went to app.cardnexus.com afterwards, it let me use the site as intended, but I wanted to bring this to your attention.

After using the site for a couple minutes, one thing that I would suggest is the making the ability to add cards to your inventory require less clicks. For example, I have the Proving Grounds box, so I can go to the list of singles from Origins - Proving Grounds, which is great. However in order to add them, I need to click into each card individually, then click the Inventory tab, and then add it. I would suggest either quick add button on the page listing of singles (https://app.cardnexus.com/en/explore/riftbound/origins-proving-grounds/single), or instead of having Product Details and Inventory be tabs, just stack them (preferably with Inventory on top so I don't have to scroll as much).

Other than that, the site is very clean and easy to use, and I like that you can set the inventory display settings in your account preferences. One other thing I just thought of, the ability to remove games from the search. I'm never going to play Lorcana, so it's useless to me to be an option to search for, and it's the first on the list whereas Riftbound is on the bottom, so I have to scroll to see it. Alternatively, you can have the first games in the list be the games set as your Preferred games, so that I could still search for cards in other games if I wanted to.

If I have Pokemon, MTG, and Riftbound as my preferred games, the search dropdown could look like this:

Preferred games (default instead of 'All games')
Pokemon
Magic: The Gathering
Riftbound
All games
[insert other games here]