Go to this website an click on Add to Firefox
Cardmarket Assistant – Get this Extension for 🦊 Firefox (en-US)
Before
Instead of the camera icon, the card's image get's displayed directly.
This change is made everywhere on cardmarket where you would see those photo camera icons, even on non-Magic pages)
Since 1.1.0: In the settings menu you can adjust the size of the Thumbnail and toggle this feature on/off
After
When you select your ManaBox file, its content gets loaded and the page automatically gets reloaded in order to fill out the page with all the necessary info.
To export your collection from ManaBox go into the top right menu and select “Export” (you need to confirm the following popup with another click on “Export”)
Then select where the export should go to. I always use Google Drive.
When on a "Singles" page, and you have loaded your ManaBox collection, a table gets created which displays which printings of the card you are currently looking at you own.
If you click on this link you will get redirected to the cardmarket Singles page of this card.
Click the “FILL” button to fill out the form.
If Condition is “MINT” a ❓gets displayed. This is to indicate that the condition of the card hasn’t been personally checked yet. A card should not be listed as MINT anyways in 99.9% of the cases.
Already listed should indicate if the card has been already put up for sale. It uses the “Misprint” metric of ManaBox (you need to update this in ManaBox yourself)