Simulator duty is not specifically mentioned in EASA FTL. However, giving and receiving training is mentioned under the definition of duty time (ORO.FTL.105, point 10 and 11). Therefore simulator time is duty time, and of course counts into the duty time limits as does any other duty time.
It is not mentioned anywhere else in the FTL or any of the accompanying soft law (GM/CS/AMC). Therefore it does not count into the block hour or Flight Duty time totals. As it is duty, any simulator time before a normal flight duty, but in the same duty period, would count as flight duty time in total. However, it would not count as a sector (kinda akin to proceeding). Simulator time after a flight duty, would count as duty, but not not as flight duty.
The FTL does not regulate ground duty very much. Yes, it does count into duty time limits, but apart from that EASA doesn't care one bit if you do two or more sessions back to back in one single duty period. And i know of some airlines that actually do schedule more than one session per period for their trainers.