Describe the problem you would like to solve
Many journals have subsections in their pages (eg, under Author Guidelines, About the Journal) and headings are required for accessibility purposes under WCAG.
The only way to add headings in content that appears on the site pages is to use the source code feature to edit the HTML directly. This requires that administrators activate the source code feature via plugin and that the editors understand how to parse and edit HTML code - that’s a high burden of support.
Describe the solution you’d like
Expose style controls in TinyMCE. I believe this is done via the style_formats configuration.
Who is asking for this feature?
Journal admins, journal editors
For a live example of where headings would be useful, see under Author Guidelines Submissions | Histoire sociale / Social History (yorku.ca). Since most OJS pages in Default theme already have a H1 declared, it may be possible to configure style_formats to only include certain styles (eg, to exclude h1).