If your heading are not numbered, you can create a dedicated Heading 2-like paragraph style to use after a Heading 1.
I assume you have modified built-in Heading 1 and Heading 2 to add the page break in the Text Flow tab and therefore are already familiar with styles. I also assume that the side style pane is visible (F11).
Create a new style called Heading 2 after H1 inheriting from Heading 2 so that any change made in Heading 2 are also forwarded to this new style. As such, you’ll only need to care for Heading 2 when tuning your document formatting.
- in the style side pane, right-click on Heading 2 and New
- in Organizer, give it the suggested name
- in Text Flow, remove the page break
- 
IMPORTANT: in Outline & Numbering, attach Outline level toLevel 2(this is the way to inform the TOC engine this paragraph is part of the outline)
When you have a level-2 heading immediately after a level-1 Heading 1, style this heading as Heading 2 after H1 instead of simply Heading 2.
To show the community your question has been answered, click the ✓ next to the correct answer, and “upvote” by clicking on the ^ arrow of any helpful answers. These are the mechanisms for communicating the quality of the Q&A on this site. Thanks!
In case you need clarification, edit your question (not an answer which is reserved for solutions) or comment the relevant answer.