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.
Thank you for posting this idea. We do recognise this as a method that can be helpful to designers. In essence it requires a segregation of the design from the analysis. The benefit that the current method offers is that this is a single one click process to perform both analysis AND design. That means that the design results are always consistent with the analysis results. However as you point out there are certainly times when being able to iterate though alternative design solutions wont impact the analysis results and thus having the analysis results retained can expedite the overall design process in some cases. The goal would be to provide the best of both worlds, ensuring that changes in the analysis includes updating designs, but also offering designs that dont trigger unnecessary new analysis.