6 files declare their use of FormTrait in Markdown 8.2

ExternalLinkExtension.php in src/Plugin/Markdown/CommonMark/Extension/ExternalLinkExtension.php

FilterMarkdown.php in src/Plugin/Filter/FilterMarkdown.php

FootnoteExtension.php in src/Plugin/Markdown/CommonMark/Extension/FootnoteExtension.php

MentionExtension.php in src/Plugin/Markdown/CommonMark/Extension/MentionExtension.php

ParserConfigurationForm.php in src/Form/ParserConfigurationForm.php

SubformState.php in src/Form/SubformState.php