So much has been written for many years about plain legal language all around the world. Here are articles, Web page, books from plain language experts or scholars that may interest you.
A Manual of Style for Contract Drafting (2017)
Author : Ken Adams
“It’s the only authoritative guide to the building blocks of contract language, and it’s in widespread use internationally. In this review, the Law Society Gazette says it’s “extraordinary.” The first edition was published by the American Bar Association in 2004; the fourth edition was published in 2017.”
Source : https://www.adamsdrafting.com/writing/mscd/