Staad.Pro has tools to select member sections, but even those are not optimum, and custom selection of a member section by hand may be more precise. But changing by hand and re-analyzing all the structure is very time consuming.

The idea is to be able to locally select/change the member section or design parameter without losing the analysis results. Carry out a local design check of that member. If final result is good, we proceed to analyze all the model for proper mechanical elements. Afterwards, is possible to have a fail member again but most of the time it won't have a radical change in stiffness and distribution of forces.