Is it possible to integrate my Trello-Board or Trello-Card in eM Client to see my Cards or add new Cards?
eM Client is able to sync Messages (POP3, IMAP, Exchange), Contacts (CardDAV, Google, Exchange, etc.), Calendars (CalDAV, Google, Exchange etc.) and Notes (Exchange, IceWarp).
Unless your cards are available as one of those, they will not be available in eM Client.