Extracting beam end forces from model containing generated loads using Open STAAD

It is possible.
You need to use the Open staad function function to extract those output values.
For extracting the beam end forces you can use the function "Output.GetMemberEndForces"

Can you elaborate the term "Generated loads"? Do you want to extract the forces for moving loads or for load combination cases generated using the auto-load combination option?

If the model contains loads that are applied using Load generation command. For Example vehicle loads on Bridge