open your theme (only read) do not directly change. (always backup before changing)
Look as example for something like {MENU= number lets say 22) this is code that handles the 'blocks (cq areas).
Sidenote : these also can get styling.
Create a similar code {MENU=25} (number has to be higher than the ones existing!!) Put in somewhere you want it to appear.
Before you do this > go to admin > menus This should give you a visual interpretation on which layout where such area is present (use this as a guideline where it has to be).
These areas get their content from 'stuff' from the left side selectable items (click use area choice..)
When your own menu area appears is should be visible in that view.. (positions can be changed up.down before after etc..) and visible on a certain page etc.. hope it helps you along..
Success more on subject: https://e107.org/developer-manual/theme-basics
Sidenote: the system also uses custom menus and are called by CMENU=.. (another story).
PS save in form > utf8 Unix code without BOM (when using editors) on pc.(Nptepad++, PSPad or others.
here's an copy out of Ewl theme line 568+ which happens in the layout : classic_lefty_wide
<div class="col-lg-6">
<div>{MENU=5}</div>
</div>
<div class="col-lg-6">
<div>{MENU=6}</div>
</div>
This means in theme php there are 2 areas by class col (column) lg (large >992px) grid 6
Since a grid here contains 12 columns it will be divide into 2 equal parts by grid 6 (each has 1/2 of the viewed page).
Working like (add similar areas just below, remember the number use!!.
<div class="col-lg-6">
<div>{MENU=5}</div>
</div>
<div class="col-lg-6">
<div>{MENU=6}</div>
</div>
<div class="col-lg-6">
<div>{MENU=7}</div> <<<<<<<<<<<<<
</div>
<div class="col-lg-6">
<div>{MENU=8}</div> <<<<<<<<<<<<
</div>
This would create 4 areas (2x2) on top of each other pasted using the lines 568 to 579 (and leaves (now) line 580 intact (being the start of the new container.