How do I edit Minuum's custom dictionary?
http://support.minuum.com/forums/210127-minuum-support/suggestions/4099381-options-to-view-edit-remove-dictionary:


  We've now added support for backing up (importing/exporting) your data
  by going to Minuum settings and choosing "Backup your data", which
  will save a file to your Downloads folder.
  
  You can still remove words from the dictionary by long-pressing on
  them when they appear in the word suggestions bar at the top of the
  keyboard.
  
  We're still working on making it easy for you to directly edit your
  dictionary on your device.


– The Minuum Team (Admin, Whirlscape) commented  ·  August 15, 2013 20:59

So, since I can both delete words and add new ones, and as long as this feature is not properly implemented, I'd say that's it.