"作文字形移动" can be translated into English as "character movement in composition writing" or, more contextually specific, if referring to the visual or typographical arrangement of characters in a composition (like in calligraphy or graphic design), it could be "typographic/character movement in essay composition" or "the shifting arrangement of characters in composition writing".
The most precise translation depends on the exact context and intended meaning. If you're referring to the dynamic or visual effect of characters moving or changing position within a written composition (perhaps in a digital or artistic context), "dynamic character movement in composition" or "visual repositioning of characters in written work" might also be appropriate.