You can call LH, but that would really be playing things extremely safe: first of all, there is no such thing as merging itineraries", all they do is put a remark into one booking referencing the other - which is not necessary because LH stations have access to your bookings one way or the other; BLR will be able to check you in for CDG, CDG will be able to check you in for AMS, just as AMS will be ab