Any Idea What This Bit Called?

User31

The first several lines of inspector tool for the 'Parent' sez: <div class="IndexPage"><div><div></div></div><div class="container"><div class="sideNavContainer"><nav class="IndexPage-nav sideNav"><ul><li class="item-newDiscussion

And it says the same for the 'Inner', but with the addition of: <div id="content"> at the beginning.

I'm assuming the name of the area in question, is possibly one of these div things:
.container ?
.sideNavContainer ?
.IndexPage-nav sideNav ?

Subarist

User31
The CSS is the visual effect of various elements stacked together. It's challenging to pinpoint the exact name of the area in question. Most of the layout spacing is primarily affected by parameters like margin and padding, which depend on the combined settings of all related elements. For your current page, if you remove the following CSS, the layout may revert to being centered.

.container {
    /* position: relative; */
    /* right: 30px; */
    margin-left: 30px;
    width: auto;
    transition: margin .3s ease-in-out, padding .3s ease-in-out, width .3s ease-in-out;
    margin-right: 30px;
}

.container {
    margin-right: auto;
    margin-left: auto;
    /* padding-left: 15px; */
    padding-right: 15px;
}

User31

Subarist Thank you!

We shall henceforth call that bit—wherever it may appear—an: 'Elemental Stackomaly', a class 3 chaotic neutral pain in the a$$.

Also, tthhaannkk yyoouu² for this:

.container {
    margin-right: auto;
    margin-left: auto;
    /* padding-left: 15px; */
    padding-right: 15px;
}

It dealt with the weird zoomy thing.

😅...except now...

...the DList is back to being anorexic again...😂gott dangit!