Level 4 Sinner Rogue with Gun-Mage Adept Feat

I'm currently playing a campaign through the Crooked Moon as a Level 4 Sinner Rogue, whose entire premise is to use Hex Magic to magically enhance Playing Cards, or a Weapon of your choice. But they don't get actual magic, i.e. spell slots. So, I thought let's give this guy some real magic. As my level 4 Ability Score improvement I choose Gun-Mage Adept, which gives me +1 Dex, Ranged Martial Weapon Mastery, The Cantrip Finger Guns (the real purpose for taking this feat), and a list of ALWAYS Prepared spells using Int as my Spellcasting Modifier. Now this gives me real magic, but not spell slots, no feat can give you spell slots from what i can tell, not even from the new Arcane stuff. So, I thought, well, let's look ahead a bit and see what i can Multiclass into, some kind of spellcaster like class.... Gunslinger Subclass Spellslinger, not only does this boost my finger guns, but it also gives me spell slots (YAY). Only.... now that I got spell slots, my Known Spells from my Rogue's Ability Score are not showing up. Spells I am supposed to always known, just couldn't cast. Now that I can cast them, they aren't showing up as known spells, and yet. When I look at my Manage Spells from the character sheet perspective, it shows a little + sign in a circle that when moused over straight up says Gun-Mage Adept. So, the system can see that I should know the spells but won't actually display them on my character sheet.