Help with a Vecna Rogue archetype

[eldamir]

My DM has gotten me hooked on the homebrew options over on middlefingerofvecna and for my roglock, I've managed to put the majority of the two variants that I'm using (The Wild Hunt patron and Spell Thief rogue archetype) into Hero Labs, but have run into a bit of a road block with Spell Thief.
I copied the Arcane Trickster to create Spell Thief, but the spell progression of Spell Thief is more like that of a warlock than how Arcane Trickster does it. I haven't been able to figure out how to set spells known and spell levels within the Class Special along those lines.

TIA