While using BiS to compare items
Specifically the crafted item “Illuminating Pillar of the Isles” above i408
I have crafted level all chosen and crafted quality 5 selected but still don’t see it in the drop down.
That doodad will let you choose more variants of the item.
In addition, to confirm that BiS is indeed considering that item, turn down your Mythic+ level to something low, e.g. Mythic 10, then re-optimize. You’ll see that it picks the 418 version of that crafted item since it is now better than the alternatives from M+.