private static Font createEditorFont( int sizeIncr ) {
		int size = UIManager.getFont( "defaultFont" ).getSize() + sizeIncr;
		Font font = FontUtils.getCompositeFont( FlatJetBrainsMonoFont.FAMILY, Font.PLAIN, size );
		if( isFallbackFont( font ) ) {
			Font defaultFont = RTextArea.getDefaultFont();
			font = defaultFont.deriveFont( (float) size );
		}
		return font;
	}
A pane that supports editing FlatLaf themes.

@author Karl Tauber
flatlaf-theme-editor/src/main/java/com/formdev/flatlaf/themeeditor/FlatThemeEditorPane.java