So, you added a card to one Collection, but decided it would make more sense to keep it in a separate Collection?
Don't worry, we got you!
1) Pick the card you want to move. Then click on the Options Menu (three vertical dots icon) on the top right. [Labeled "1." and circled in orange on screenshot below.]
2) Click "Edit Card" on the drop down list. [Labeled "2." and squared in orange on screenshot below.]
3. A new screen will pop up to "Edit Collection Card." Here, you want to choose the Collection drop down [squared and starred in orange in screenshot below.]
4. After you click on the drop down, all your Collections will be listed. Now, choose the new Collection you would like to move this card to. [Example circled below in orange.]
5. Lastly, don't forget to hit Save to update your Collections. [Squared in blue above.]
Happy Collection Management! Nice job in keeping the important things organized.