If you’ve played Fallout, you’ll remember that “Tagging” a skill allows it to increase at a faster rate than other skills.
Although it is hidden in the UI, just due to some bad UI decisions, you can also tag skills in BaK to make them increase faster. Right-click on a character portrait to see the skill screen. Below each skill is a sword with a gem in the hilt. If you click on the gem, the gem colour will change to indicate that the skill is now tagged.
Now, when a tagged skill is used, it will increase faster than non-tagged skills. (And fwiw, tagging all of the skills or too many of them doesn’t work.)