You would only need 2 columns? First column 2/3 with a pages section and a fields section, and a second column 1/3 with a files section.
Something like:
title: Default
icon: document
columns:
one:
width: 2/2
sections:
calendars:
headline: Subpages
type: pages
status: all
layout: list
limit: 10
info: "{{ page.tags }}"
sortable: false
templates:
- default
fields:
type: fields
fields:
meta_title:
type: text
description:
type: textarea
text:
type: textarea
attachments: fields/attachments
tags:
type: tags
index: siblings
two:
width: 1/3
sections:
files:
type: files
template: sometemplate
Note that you cannot have a field called title
in your blueprints. The title is a special field that must not be entered in the blueprint.