Is it possible to export content of subtrees without their headings?

Question

I draft documents in org-mode and export them to LaTeX, HTML, etc. as needed. I frequently use the tag :no_export: whenever I don't want a certain subtree to show up in the output.

What I also want is want is for the export to completely ignore certain subtree headings, but not to ignore then content of the subtree under that heading. In other words, certain subtrees should be exported as if their content were just a continuation of the parent, instead of having its own subtree.

I'm ideally imagining a tag like :no_title:. I want my org-mode outline to look more or less the way I am used to. But I would consider other approaches with similar results.

To illustrate, here is a MWE of a document drafted in org-mode.

* Chapter 1
** Section 1
*** Paragraph 1      :no_title:
First paragraph of text in the section.
*** Paragraph 2      :no_title:
Second paragraph of text in the section.
* Chapter 2
** Section 1
*** Subsection 1
**** Paragraph 1      :no_title:
First paragraph of text in the subsection.
**** Paragraph 2      :no_title:
Second paragraph of text in the subsection

When I export that currently, I get something like this:

1 Chapter 1

1.1 Section 1

1.1.1 Paragraph 1 :no_title:

First paragraph of text in the section.

1.1.2 Paragraph 2 :no_title:

Second paragraph of text in the section.

2 Chapter 2

2.1 Section 1

2.1.1 Subsection 1

◊ 2.1.1.1 Paragraph 1 :no_title:

First paragraph of text in the subsection.

But what I want is more like this:

1 Chapter 1

1.1 Section 1

First paragraph of text in the section.

Second paragraph of text in the section.

2 Chapter 2

2.1 Section 1

2.1.1 Subsection 1

First paragraph of text in the subsection.

Answer 1

This may be a preferred way (due to its simplicity) of accomplishing your goal -- it seems to have gotten buried in the comments of another answer:

1. Add the following to your .emacs file:

    (require 'ox-extra)
    (ox-extras-activate '(ignore-headlines))
   

2. Use the ignore tag on headlines you'd like to have ignored (while not ignoring their content)

NOTE: currently, add-on ox-extra becomes available after installation of the package org-contrib.

OLDER NOTE: if you are using ELPA to install org-mode, you must add the org-mode repository to your list of ELPA repositories. See here for more details. After this is done, refresh the package list (M-x package-refresh-contents) and install the org-plus-contrib package (e.g. with M-x package-install). Don't forget to get rid of any old org-mode installations.

Answer 2

Yes, this is entirely possible. Add the following code to your init-file:

(defun org-remove-headlines (backend)
  "Remove headlines with :no_title: tag."
  (org-map-entries (lambda () (delete-region (point-at-bol) (point-at-eol)))
                   "no_title"))

(add-hook 'org-export-before-processing-hook #'org-remove-headlines)

Acknowledgments

This question has been asked on StackOverflow before (with a different focus and wording, which is probably why you weren't able to locate it when you searched the internet before posting here). The code above is a simplified version of the code in the accepted answer; it works for the new exporter introduced in org-mode 8.0 and is backend-agnostic.

Update

As discussed in the comments, the code above causes contents of entries tagged with :no_title: to disappear if they are preceded by an entry that is tagged to be excluded from the exported document. For example, exporting the following document will produce a document with a title and TOC, but no content:

#+EXCLUDE_TAGS: no_export

* No export                          :no_export:
  This is not meant for you to see.
* No title                           :no_title:
  You should see this.

The reason for this is that org-mode removes the headline tagged with :no_title: before it removes the entry whose headline is tagged with :no_export:. As a result, when it gets around to removing the no_export entry, it treats contents of the no_title entry as belonging to the preceding no_export entry. This makes perfect sense because there is no structural element (heading) that separates the contents of the original entries anymore.

To solve this problem, we can transfer responsibility for removing no_export entries to org-remove-headlines. This way, we make sure all no_export entries are gone before headlines are removed from no_title entries:

(defun org-remove-headlines (backend)
  "Remove headlines with :no_title: tag."
  (org-map-entries (lambda () (let ((beg (point)))
                                (outline-next-visible-heading 1)
                                (backward-char)
                                (delete-region beg (point))))
                   "no_export" tree)
  (org-map-entries (lambda () (delete-region (point-at-bol) (point-at-eol)))
                   "no_title"))

(add-hook 'org-export-before-processing-hook #'org-remove-headlines)