Spellcasting in Homebrew

Hello, I must ask the specialists, because even AI cant help with it. Is there any way I can homebrew Arcane Trickster with full wizard spell slots and spell level progression? Like No matter what I do, ticked “Level” in “Spell Prepared Type”, or tried to grant the Spellcasting feature at level 1. It just doesnt seem to work and the “Extra magical Arcane trickster” is still just a ⅓ of a wizard.

First, why do you want a full caster Rogue? Unfortunately, D&D Beyond's homebrew system is very stupid, so this cannot be done.