From pattern +‎ -er, with either the verb or the noun pattern.^[1]

patterner (plural patterners)

1. Someone who or something which makes or uses a pattern.
   • 1972, Ursula Le Guin, The Farthest Shore, page 14:

     Between two tall blades in the clearing a spider had spun a web, a circle delicately suspended. The silver threads caught the sunlight. In the center the spinner waited, a gray-black thing no larger than the pupil of an eye.
     “She too is a patterner,” Ged said, studying the artful web.

   • 1988 April 8, Robert McClory, “Come Back: The Rehabilitation of Meg Tippett”, in Chicago Reader‎^[1]:

     When her head and trunk are turned right, her left leg and right arm are bent and her right leg and left arm are straightened out. When she is shifted to the left, legs and arms are moved in the opposite direction. The movements, called cross-pattern patterning, simulate the motion a normal body experiences effortlessly when it is walking. […] When Mike finally calls "time," she is sweating and panting, and so are her father and the other patterners.

   • 1996, Hannes Fischer, Method and system for producing a stencil by storing color files and creating the needed bit sequence, US Patent 5,822,209 (PDF version):

     1. A method of producing a rotating, clamped stencil on which a pattern is produced by a patterner comprising the steps of:
     moving a patterning head of the patterner relative to the stencil; […]

2. Something which follows a pattern, or may be identified as part of a pattern.
   • 1995, Joachim Jacobs, Syntax, page 1052:

     the terms object patterners and verb patterners will be used here for those elements whose order tends to correlate with that of the object and verb respectively. Thus genitives are object patterners while the nouns they modify are verb patterners.

• repattern