I just realized that on the PC character sheets, there is a subsection called Custom Skills, with appropriate places to upgrade ranks in them as well. Were these built in as a contingency for future updates to the system, or could I have let my PC's imaginations run wild with it as long as they paid the appropriate non-career cost of the upgrades? Honestly, I don't know how that didn't catch my glance earlier, or any of my PC's for that matter.

Edge of the Empire Core Book, page 102, big block at the bottom of the page.

It's more there for house rules, which would generally be written by the GM with approval from the players. You might want to add skills like music, culinary, art, or whatever. Perhaps a throwing skill for grenades? Maybe memory? You could give it to your PCs as a career skill if it made sense for their background.

Probably the most common use is to add a lightsaber skill when playing with just EotE rules; other skills limited to specific books get added a lot too.

Every so often you see a character specific skill, like cooking.

Cybernetics is suggested in the Special Modifications book too. It's just one example of the developers expecting groups to tweak the system to their personal tastes.

17 hours ago, KamaKrazyWarBoy said:

I just realized that on the PC character sheets, there is a subsection called Custom Skills, with appropriate places to upgrade ranks in them as well. Were these built in as a contingency for future updates to the system, or could I have let my PC's imaginations run wild with it as long as they paid the appropriate non-career cost of the upgrades? Honestly, I don't know how that didn't catch my glance earlier, or any of my PC's for that matter.

Yes.