Usually a community search should find multiple posts on this already.
I therefore updated the Skype for Business FAQ to contain this information already in the text and the post itself in addition to the Admin Guide outlines this clearly:
Jan 04, 2016Question: Can I change / re-assign the appearance of a Line and / or Presence Keys?
Resolution: Please check => here <= and the limit using EFLK is 100.
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
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