If character has more skills and traits, than 'Skills' tab can fit, what happens with overwritten traits and skills:

a) Disappear;
b) Character still have them and benefits, but can't see and increase;
c) Any possibility to expand 'Skills' window to see rest of the list;

???

As far as any of us have been able to figure out, it's "B". No plan has been made by HPI to expand the skills window. I just keep track of my traits on a separate piece of paper so I remember who has what.

Best solution: Only train in those skills which you absolutely need.

-Sazerac

Note that you still can increase skills at the guilds, even when they're not visible.