I dont think its possible to add pickups directly. However, you can get the coordinates in build mode, and then add the pickup manually to the config.ini. Save coordinates for example to a class , then copy coords from savedpositions.txt to the config.ini:
; -----------------------------------------------
; <<<<< START OF PICKUPS >>>>>
;
; Pickup = #Pickup_id #spawn_x #spawn_y #spawn_z
;for example
Pickup = 368 -855.5118 -631.2861 11.3756