Check section 5.15 Redefinition of Joint and Member Numbers of the OpenSTAAD help (C:\SProV8i SS6\STAAD\Help\OpenSTAAD.chm)
Substitute
Joint and member numbers may be redefined in STAAD through the use of the SUBSTITUTE command. After a new set of numbers are assigned, input and output values will be in accordance with the new numbering scheme. This facility allows the user to specify numbering schemes that will result in simple input specification as well as easy interpretation of data.
You can, of course, also do this with the STAAD.pro user interface using Geometry menu - Renumber...