Symptoms

Right-Click (Context Menu) Not Working
 

Diagnoses

Known issue with IE11.
 

Resolution

Running IE in IE10 document mode allows right-clicking again. Workaround to apply this to all designers:

Force IE10 Document Mode by modifying the 'X-UA-Compatible' HTTP Response Header on the K2 - Designer site in IIS. The current value was "IE=11,IE=10,IE=9,IE=8".  Next, run an 'iisreset' and clear your browser cache.  Removing 'IE=11' forces Internet Explorer into IE10 Document Mode for Designer SmartForms, which should resolve this issue.