CoreRPG is pretty much vanilla and allows a base for people to do their own rulesets or basic setup. As such, there is no library of skills and abilities as there would have to be a different one for each of the many different RPG systems.
You can make your own library of skills/abilities - but you have to do this by manually creating the XML.
Or, you could create a Story entry and make links to various abilities - using this as a library of sorts. You can drag abilities to a story entry from a character sheet - so set up the abilities in the character sheet and drag/drop them in a story entry. Although you'll need to keep the character sheet in the campaign, as the link will refer to that character sheet.
Quite a few people create character sheets for the specific RPG system they play - and use these as templates or sources of drag/drop data. There are lots of example character sheets here:
https://www.fantasygrounds.com/forum...aracter-Sheets
Or, you may want to look at MoreCore - this has the concept of custom "rolls" that you can create with descriptions (and rolling mechanics if needed). These can be exported to a module. Find MoreCore here:
https://www.fantasygrounds.com/forum...reCore-Ruleset