Manuscript supports integrating directly with Trello to link your Trello cards with Manuscript cases. You can enable it for your team in the Avatar Menu -> Integrations.
This integration is the same one that you love from FogBugz. Everything you need can be found over at the Trello PowerUps page.
Once you enable the PowerUp for a Trello board, you’ll see a Manuscript icon on each card on the board. Click that for an easy-to-use search bar to help you find your Manuscript case. Alternatively, case URLs can be dragged into a card and will be added automatically. Once cases are added to the card, they will show the case number and name, amount of time remaining or status, assignee, and time of the last edit. The front of the card will show the number of cases with a Manuscript logo.
You can read more about integrations here.