
Hi @Anita ,
According to my research and testing, unfortunately, there is currently no way to insert subtitles or text in SharePoint modern page.
As a workaround, you can achieve it by changing the library to classic page, please refer to the following steps:
1.Go to Library settings ->> More library settings ->> Advanced settings;
2.Choose Classic experience and click OK, then return to the library and refresh;
3.Click the gear icon, Settings ->> Edit page
4.Click Add a Web Part ->> Media and Content ->> Script Editor ->> OK
5.Click Edit Web Part
6.Click EDIT SNIPPET ->> input the following code ->> save
<span style="color:red;font-size:20px">this is a test</span>
7.Click OK and Stop Editing
My test result:
Hope it can help you. Thanks for your understanding.
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