Tent of Witnesses

Some views of heaven in Revelations are strange, to say the least.
Rev 15-1 After this, I looked, and the sanctuary of the tent of witness in heaven was opened. The seven angels come out of this sanctuary. The Greek says, “temple of the tabernacle.” They pour out their bowls. Then there is an odd statement: ‘And the sanctuary was filled with smoke from the glory of God and from his power, and no one could enter the sanctuary until the seven plagues of the seven angels were finished.’
Who or what are the witnesses? You only have two groups mentioned: The seven angels and the people who have come out of the tribulation. The angels are doing the deeds, so they are not the witnesses. The two witnesses, Elijah and Moses, are already down on the earth.
He saw those who had conquered the beast, its image, and the number of its name. It sounds good until you realise they had to have died to be there. That means they are dying during the wrath, so it cannot be them. That most likely means that these witnesses are from a prior time, but it does not say when.