A short Maya script for transferring selected object transforms to their offset matrixes. Deletes old transforms after finishing. Useful for creating controllers when rigging.

xform_to_offset.py

"""
To use, paste this code into the script window in Maya. Make sure to paste it into a Python panel. 
You can then mark the entire script with ctrl+a, and middle-mouse drag it onto a shelf to create a shortcut button.
Script works with multiple selections. Simply select all the objects that you want to transfer the objects transform to their 
offset matrices on, and then run the script.

@author Frederik N. S. Larsen
"""

from maya.api.OpenMaya import MEulerRotation, MMatrix
import math

s = cmds.ls(sl=True)

for f in s:
    tX = cmds.getAttr(f"{f}.translateX")
    tY = cmds.getAttr(f"{f}.translateY")
    tZ = cmds.getAttr(f"{f}.translateZ")
    rX = cmds.getAttr(f"{f}.rotateX")
    rY = cmds.getAttr(f"{f}.rotateY")
    rZ = cmds.getAttr(f"{f}.rotateZ")

    cmds.setAttr(f"{f}.translateX", 0)
    cmds.setAttr(f"{f}.translateY", 0)
    cmds.setAttr(f"{f}.translateZ", 0)
    cmds.setAttr(f"{f}.rotateX", 0)
    cmds.setAttr(f"{f}.rotateY", 0)
    cmds.setAttr(f"{f}.rotateZ", 0)

    tMatrix = MMatrix(((1, 0, 0, 0), (0, 1, 0, 0), (0, 0, 1, 0), (tX, tY, tZ, 1)))

    eRotation = MEulerRotation (math.radians(rX), math.radians(rY), math.radians(rZ))
    rMatrix = eRotation.asMatrix()

    newOffsetMatrix = rMatrix * tMatrix

    cmds.setAttr(f"{f}.offsetParentMatrix", newOffsetMatrix, type="matrix")