Hello @Xenon ,
Welcome to Q&A Forum!
There are two solutions for your reference:
Step1:Add jQueryUI SPFX web part to your SharePoint. For more information, please see Add jQueryUI Accordion to your SharePoint client-side web part.
Step2:Using jQuery code to classic sharepoint page
- Creat a page and Edit page
- Add a Script Editor web part and paste this code: The jQuery.txt
- Now on your Page Content, Type in a sample header and click Format Text. You can choose from Header 1 - Header 4.
Thanks,
Echo Du
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