{+}Ask:
{+}Per the current design, when a customer sets up a Confluence cloud landing page as any space's overview page then they are unable to see the side bar.

For example, this URL would have a hidden sidebar:

https://example.atlassian.com/wiki/spaces/ABC/overview?mode=global

 While this URL would show the sidebar:

https://example.atlassian.com/wiki/spaces/ABC/overview

This is setup as per the design currently as the landing page should have different configuration than a space's settings thus it's intentional.

Some customers would like to have the ability to be able to see the side bar.