Must give credit where credit's due . . . a 1898 article about the dedication of Marion St. Mary's Church says that the architect of the church was John B. Verment of Massillon.
Verment apparently carved a tombstone at St. Joseph in Tiffin shown in an earlier post (third picture):
According to "Artists in Ohio, 1787-1900," Verment worked as a carver of stone and marble in the Massillon area in the mid-1880s; by 1889 he is listed as an architect.
The article also had some illustrations of the stained glass windows. Above is an illustration on the left, and on the right is how the window looks today.