“The seventh trumpet in the Revelation was not even known/revealed when Paul wrote to the Thessalonians.”
Paul DEFINITELY had some “inexpressible things” by astounding revelation. I wouldn’t presume to declare what things they were or weren’t.
“The scene revealed to John in the spirit, found in chapter five of The Revelation has The Redeemed from all nations, kindreds, tongues (that little clue says these are more than just Jews), those redeemed are in Heaven BEFORE the seven sealed scroll is even taken by the Lamb to be opened.”
No such gathering is present in Chapter 5; AFTER the scroll is taken by The Lamb, they do, however, become the subject of “a new song”:
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When He had taken the book, the four living creatures and the twenty-four elders fell down before the Lamb, each one holding a harp and golden bowls full of incense, which are the prayers of the saints. And they sang a new song, saying,
“Worthy are You to take the book and to break its seals; for You were slain, and purchased for God with Your blood men from every tribe and tongue and people and nation. ...”
— Rev. 5:8 & 9
The reference to “men from every tribe and tongue and people and nation” magnificently reaffirms the scope of God’s forgiveness, which He wrought in Christ at The Cross. This connection to “the world” and “whosoever” of John 3:16 emphasizes what Paul articulates in 2 Cor. 5:19 “namely, that God was in Christ reconciling the world to Himself, not counting their trespasses against them.”
What I did write is our presence as the redeemed is axiomatic with the scene in chapter five, as we the redeemed are singing a new song as the lamb takes the scroll and begins to open it. Chapter five has The Redeemed in Heaven when the scroll is take and the Lamb begins to open it, launching the Tribulation/Jacob's troubles.