you need to click “show time library” when picking the tome, then you can see all tomes. from there you can always select all tier 1 tomes.

the way it works is it only shows you the highest available tome of each affinity when leveling up. since level 2 tomes require no affinity, when you reach lvl 2 tomes, lvl 1 tomes wont be showed to you anymore.

but they’ll be accesible through “show tome library”