Why you might want PICKADD set to 0
PICKADD is one of those system variables that you see mentioned a lot, usually in a negative light. Somehow it gets set to 0 and then you can only select one object at a time. Who would ever want to do this, right? Although 99% of the time, you probably keep PICKADD set to 1, there is a useful reason to set it to 0. If you are editing or viewing properties of multiple entities one at a time, this can be helpful.
If PICKADD = 1 and you select one entity to view its properties in the Properties window, no problem. But what happens when you select a second entity? Of course, Properties displays the properties for both entities. You won’t get much useful info if you select say a SPLINE and an MTEXT entity. To avoid this, you have to press ESCAPE to cancel the previous selection each time.
Now, set PICKADD to 0 and then each time you pick an entity, only that one entity is selected and you can edit or view its properties.
If this is something you think might help you, consider using the following lisp code to toggle the value of PICKADD from 1 to 0 to 1 and so on.
(setvar "PICKADD" (abs (- (getvar "PICKADD") 1)))