search text in ckeditor angular component and highlight

This can be achieved using jQuery:

CKEDITOR.instances.editor1.window.getFrame().$ retrieves a native DOM element for editor editable area. So:

$( CKEDITOR.instances.editor1.window.getFrame().$ ).contents().find( anything );

CKEditor provides an API for DOM manipulation:

CKEDITOR.instances.editor1.document.getById( 'someId' );

CKEDITOR.instances.editor1.document.getElementsByTag( 'div' );

For highlighting:

Check this out :

https://ckeditor.com/docs/ckeditor5/latest/api/highlight.html

https://ckeditor.com/docs/ckeditor5/latest/features/highlight.html