Include Column in Real work allocation

You cannot customize Real Work Allocation screen with screen customization plugin.
It can customize "alomosté every screen, but not all : not real work, not planning, not topday, ...
Only screen with design with List / Detail, not including parameters screen.

But what you try to do is useless.
When you have assigned work on activity, and enter real work (and possibly reasses left work) you will automatically have completion calculated : % completion = real / (real + left)