Remove/Replace Skill
 

So here is my quandary: I want to give a rouge arcane trickster the arcana skill as a class skill.

I thought to tackle this just like I tackled the replacing languages: Using personal adjustments, remove one, add one.

My issue is that I can't figure out how the "Personal Adjustment" "Proficiency" work when the adjustment is a negative number.
- Create a new character.
- Select race, any race. Human for my example.
- select class, any class. Rogue for my example
- select a background, any background. Acolyte for my example.
- Give the rogue the first three skill proficiencies on the list. Shows one left.
- Add a "Personal Adjustment" of "Proficiency". Set to -1.
- Proficiency tab now appears. Reports: Too many skill proficiencies (one over)!

From here, I can't seem to figure out the right combination to either reduce the rogue proficiencies or replace one of the list with arcana.

NOTE: Just to avoid options that will not resolve the specifics of my actual use case, here are more details. The player this will be used for already has a custom background with 2 skills not available to a starting rogue, so the resolution here must replace one of the rogue skills, not a manipulation of racial or background skills to allow for a proficiency in the arcana skill.

Thoughts?

you can just use the Proficient skill adjustment and select Arcana from the drop down, but that just adds the skill without taking one away

What I would like to do is either:
- Allow arcana to be selected as a class skill
OR
- Add an arcana proficiency and reduce the class proficiency number by one.