A suggestion on something I truly like with Yahoo Finance:

Could we look into implementing customized "Views" for the "Current Holdings" tab, where each defined and saved "View" features a set of user-defined columns to be displayed?

Then allow the user to quickly switch b/w views via a drop-down window?

You probably could have two or three pre-defined views, and a few user-defined ones.

Whatever the user has "turned on" would be the same across all tabs at that time.