Yes easy.
There is free access to all staterooms on all decks, including concierge.
Anyone can walk through, and put things on your FE.
I think you ask, as when the Dresm first came into service there was a gate to concierge, it went quickly. The only thing that needs card access is the concierge lounge, even that, TBH, you can get in quite easy.
I have stayed in concierge on two cruises on the Fantasy, the sister ship, the only thing you may have any issue with is, cruise magnets for your door, as they are wood laminated.