I want to introduce extra placeholders to the london layout, called breadcrumb and side menu navigation. Can I write own layout that extends the london layout ?

Hi Dhana,

You can create your own customized layout. 

For that, you need to open the web block (will open a clone for Richwidgets) and copy/paste into your app.

Then, you just need to rename it and add your placeholders and customizations (css, containers, etc). Please note that there is one private that you should remove to be able to do use it - allowAddToIOSHome. Although you will loose this feature and in case you need it you need to implement "it by hand".

hope that helps,