Add subtitle

I want to enter different content like subtitle 1, subtitle 2, etc. will the subtitle be added?
What should I do?

If one uses Dorico Pro, one can edit or add a new Page Template to host an enlarged Title Field large enough to hold the Title and subtitles on separate lines or else add a new field for the subtitle tokens.

One would type the subtitles into File > Project Info to populate the tokens on the Page Template.

If I apply a new template, will the project information fields change as well?

The info in Project Info is fixed until you change it.
Thus the info should be the same in every Page Template, although each template can change its appearance (font, size, location) if desired.

The information that you enter into Project Info only appears on pages if the corresponding token exists somewhere on that page.

Here are the page templates that Dorico provides automatically. You can edit these to add the subtitle token and format it as required.

Depending on where you want the subtitle to appear, you might want to edit the First page template (for it to appear beneath the project title), the Default page template (so it appears at the top of page 2 onwards), and/or the Default flow heading template (so flow subtitles appear beneath flow titles in flow headings).

See also this labelled diagram:

Thank you.