The Collaborative International Dictionary of English v.0.48:

Manageability \Man`age*a*bil"i*ty\, n.
   The state or quality of being manageable; manageableness.
   [1913 Webster]

WordNet (r) 3.0 (2006):

manageability
    n 1: capable of being managed or controlled [syn:
         manageability, manageableness]

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "manageability":
   adaptability, compassability, controllability, convenience,
   corrigibility, domesticability, ductility, feasibility,
   flexibility, governability, handiness, housebrokenness,
   malleability, manageableness, maneuverability, manipulability,
   manipulatability, negotiability, operability, performability,
   pliability, pliancy, practicability, practicality, tamableness,
   tameness, untroublesomeness, viability, wieldableness, wieldiness,
   workability