Pathfinder 2e's Dual-Class Characters variant rule, run on two real class items on the character sheet rather than merging two classes into a single item ahead of time. That is where the name comes from, and it is the whole design: both classes stay real to the system, so feats and rule elements that check for a class still work for the second one.
A Fighter/Wizard gets the Fighter's Hit Points and armor and weapon proficiencies, the Wizard's spellcasting proficiency, the better of the two in every saving throw, both class DCs, both key attribute boosts, and a separate feat ladder for each class.
What it handles
- Every proficiency at the better of the two classes, and Hit Points at the higher die rather than the sum.
- A class DC for each class, at each class's own key attribute, with one marked primary.
- Both key attribute boosts, with a row per class in the Attribute Boosts window so each writes to its own class.
- A class feat ladder per class, at the levels that class grants them. Skill, general and ancestry feats stay on one ladder, since the variant rule allows those only once per level.
- Class features from both classes, granted on level up and removed on level down, plus a Sync action for a class added after 1st level.
- A trained skill counter at 1st level, using the larger of the two classes' additional skill counts rather than the sum.
- Ancestry Paragon as a separate world setting, folded into the system's own Ancestry Feats group rather than adding a second ladder.
Nothing is precomputed. The numbers are recalculated from the two class items every time the character is prepared, so turning the module off or removing the second class returns the character to exactly what it was.
Requires libWrapper. Verified against Foundry v14 and Pathfinder 2e 8.4.1 and 8.5.0.