When creating a card in a Custom Collection, unless it matches the filters of the current collection it might seem to disappear after you've finished it. It's not gone don't worry, it's just no longer applicable to that current collection.
Match new cards to filters
By default we don't try to match up cards to collection filters as they can be complex and you might not want new cards to appear in that collection. You can change this in the Noteboard options menu, by enabling the match new cards to filters.
This will attempt to add as many attributes to a new card when you start creating it. e.g. if a collection like the one above filters by cards with #discussion, then any new card created within the "Discussions" collection will automatically inherit #discussion.
Not all cards will display in a collection
If you don't have the Match new cards to filters enabled, or if you add an attribute to a card that's not filtered within that collection, the card may seem to disappear, but you will be able to find that card again in your Home. Either click Home in the sidebar or press "Cmd / Ctrl" + "Shift" + "H" on your keyboard to immediately go Home.
We've added a little helpful yellow indicator when authoring cards in Collections to remind you that this might happen :)