[Bug?] Needs to be positioned next to page content

[rubaboo]

In otherwise vanilla Firefox, this would only be relevant when the Second Sidebar is on the left, since native sidebar is also on the left.

However, I am using Second Sidebar with Waterfox, which also has "Tabs Sidebar" that can be positioned left or right. Therefore I am asking for Second Sidebar to be positioned not simply "to the right" of the other sidebars, but immediately adjacent to the browser page content:

First sidebar(L)	Second Sidebar(L)	Regular browser page content

Regular browser page content	Second Sidebar(R)	First sidebar(R)

Nothing needs to change when the two sidebars are configured to be on the opposite sides, of course:

First sidebar(L)	Regular browser page content	Second Sidebar(R)

Second Sidebar(L)	Regular browser page content	First sidebar(R)

Basically, I would like to see the web panel content and the main page content side-by-side, without other sidebars getting in between.

FYI: The current state in Waterfox with both Tabs Sidebar and Second Sidebar on the left: