Scene split without splitting the chapter

I want to split a few of my chapters into two scenes but don’t want to split the chapters.

Is there any particular way I can do this with a symbol, multiple EM dashes or multiple underscores, etc.?

First book so not quite sure how to handle this.

It depends; if you’re just doing it for yourself, then use whatever you like; <<<>>> ## **** … etc.
If you’re formatting for submission to a given publication, you should see if they want you to use a certain separator and use that.

Separators are usually centered, so do that,and then select that entire line and select Format->Formatting->Preserve Formatting to prevent the alignment of the separator from being left-justified by the compile process.