I actually just figured out that it adds it to the sheet automatically when you pick Rogue as your class. I think it's confusing because the Criminal background still lists it as a suggested proficiency, but it's not on the drop down list because you already have it.
Basically there are no tool proficiencies for Thieves' Tools
Also noticing this just now.
They should be there. If not, could post the link to your character?
I actually just figured out that it adds it to the sheet automatically when you pick Rogue as your class. I think it's confusing because the Criminal background still lists it as a suggested proficiency, but it's not on the drop down list because you already have it.
Ah yeah i see that now. I thought that meant i'd automatically have thieves tools in my inventory at the start.