Functions Menu Select:

select obj from objID key obj-ID's (separeted with blanks) - eg 'P20 S21' - objects will be hilieted and - objects will be added to group; (eg file only group-objects with Group/save Group => File) Clear hilite and group with Esc-key.
Select group of objects with box: press Ctrl-key and left mouse-button, keep both pressed, move mouse ..