Running out of storage space is not a question of 'if' but 'when'. But how to avoid being overwhelmed by chaos? The answer is SORTING! When fencing, press keys while selecting something from a combobox on the top left:
>CTRL+LMB: by total size.
SHIFT+CTRL+LMB: by unit size.
ALT+LMB: by total value.
SHIFT+ALT+LMB: by unit value.