How can I find out the maximum nodal displacements for a group of nodes ?

OR

How can I find out the maximum support reactions for a group of supports ?

OR

How can I find out the maximum Beam stresses or Beam forces for a group of beams ?

OR

How can I find out the maximum plate stress for a group of plates ? 

To find out the maximum response ( nodal displacement, support reaction, section forces, beam end forces, beam stresses, plate stresses etc. ) out of a group of entities, you should first go to the Post processing mode. Select the entities ( could be nodes, beams or plates depending on what you would like to do). In STAAD.Pro Connect Edition, go to the Reports menu on the right and choose any one of the appropriate item as shown below. The corresponding option for older versions is shown at the end of the wiki

A dialog box will pop up where you can define a sorting criteria, select the load cases and even save the report by a certain name. In the screenshot below, the beam section forces are going to get sorted by MZ moment

A table would pop up where the data would be sorted based on the sorting criteria. In the screenshot below you can see that the data is sorted based on Mz.

 In older versions of STAAD.Pro ( v8i ), the reports are available at the location shown below