KiCAD allows this, but doesn't really - for lack of a better word - support you with inbuilt tools to actually do it (yet).
There is work being done - from what I read in this forum - which goes towards making this easier, but it will take a while (example: new component selector).
I think @devbisme had some external python scripts that are able to provide you with csv or xls formatted content of symbol libraries, that you then can modify comfortably with OpenOffice/Excel/etc. and import back into the libraries (works even with project schematics, that's actually where it originated from).
There was another tool that (I think) did run inside KiCAD, but I don't know if it's still working - was roughly 10 months ago I think.
Ah, here you go..
Personally I created my resistor/capacitor libs with external python scripts from scratch and most other parts as I did go along, at some stage even editing the libraries directly via a text editor.
Things you want/need to do:
Add similar fields - read through this "Standard symbol field names initiative" and see what fancies you. Set the Default Value as underscore or whatever - don't leave it blank, otherwise this field isn't added when you change parts in the library or add them to your schematic.
Existing parts in the lib won't get those fields automatically. I hope one of the tools I mentioned do that. If not, either python scripting or text editor..
Make sure you understand how symbol and footprint libraries are maintained. They're different for the foreseeable future.
If you do personal atomic libs, you run them locally and probably want to set up KiCAD along these lines (older post of mine, with some outdated info):