Hi @swati_ka5
I assume you want to add common styling to each topic/sub-topics' titles. To achieve this type of use cases, you can download the temporary files and check the classes corresponding to each topic heading level. Then, add a common styling based on your requirements.

For example, If I have <h1>, <h2>, & <h3> levels for each topic and sub-topic then those headings should have .title.chapter.topicref as the common class (refer screenshot), then in content.css you should add something like below to apply the common styling.
.title.chapter.topicref {
font-size: 20pt;
font-weight: bold;
color: #666;
}
Do try this and let us know if it works.