Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
tractābĭlĭtas, ātis, f. [tractabilis], fitness for being handled or wrought, manageableness, tractability (very rare): populus, salix, tilia in sculpturis commodam praestant tractabilitatem, Vitr. 2, 9, 12.