In a structure which has wall panels in addition to other things, is it possible to temporarily disable some of the outer panels and analyse just the rest of the structure consisting of interior beams, columns, and slabs?
STAAD has an INACTIVE MEMBER command. This command can be used with beam/columns as well as plate elements. The members and elements subjected to this condition will have their stiffness, as well as any applied loading on them, ignored. This means, only the remainder of the structure will be treated as being active. So, what you can do is use the INACTIVE MEMBER command in conjunction with CHANGE to create a multiple analysis model.
In this manner, a single STAAD input file can represent various stages of construction of the structure. Take a look at example 4 in the Examples manual. Although that example illustrates the procedure using just beams, the same can be used with plates included in the structure.