This page-template has a offcanvas-sidebar.
The width of the sidebar dynamically changes depending on the content inside the sidebar and main area.
On mobile devices the sidebar gets moved into an offcanvas menu. (resize this page to see the effect).
Block areas:
There is a bug where adding blocks to the offcanvas-sidebar is sometimes not visible or appears not to be added.
It is getting added, its just not visible.
Publishing the page and re-entering edit-mode fixes this.
If you want to add a content-block simply add it to another area and move it to the sidebar area.
I am still investigating the issue.
This is inside the right sidebar.