Outline folding mode
Added a new Writer outline folding mode (as experimental feature). You should enable experimental features in Tools ▸ Options ▸ LibreOffice ▸ Advanced dialog to see "Show outline content visibility button" checkbox in Tools ▸ Options ▸ LibreOffice Writer ▸ View dialog. After checking it you'll can see a button with arrow near any selected heading in your document. Click on it to fold all text from the current heading to next heading. Right click on it to fold all text from current heading to next the same level heading with all its subheadings
