Sidebar toggle needs better dimensions and clearer visibility

[bipplane]

Is your feature request related to a problem? Please describe.
The sidebar is mostly camouflaged inline with the rest of the page background, with only an arrow symbolising that the left panel is collapsible. The clickable area is also quite wonky (see screenshot for details)

Describe the solution you'd like
A sidebar that is visible at a glance, and clearly shows where it is clickable from.

Additional context

Current Look

Actual Dimensions

Blue is where you can click the sidebar, and Red is the padding; the dimensions seem quite awkward.

[Arif-Khalid]

I think this is a valid concern and the linked PR is appropriate. Any concerns @CATcher-org/active-devs