AMA Manual of Style - Stacy L. Christiansen, Cheryl Iverson 2020

Appendixes
Manuscript Preparation for Submission and Publication

Some journals publish appendixes, at least occasionally, for material that might be considered ancillary to the content of the article itself (eg, derivation of a complex formula used in the article, a survey instrument used in a study, statistical modeling details). The JAMA Network journals generally do not use appendixes. If the material is worthy of inclusion because it contains important information, it could be considered for online supplemental content (see 2.12, Online-Only [Supplementary] Material).

Information contained in appendixes becomes part of the article; it is published under the imprimatur of the journal and therefore should undergo editorial evaluation and peer review and should receive the same attention to detail in the editorial and production processes as the main body of the article.