Editing the Innovation Theme Core Files

[Connie]

Even when the wiki says:

As of 3.1, you can force the page editor's “Template” dropdown to ignore partial template files by naming them with a .inc.php extension. For example, a user will not be able to choose footer.inc.php as a page template because it's file extension will prohibit it from ever showing in the select box.

this is not correct. All files with the extension .php are listed ;=)
1)
it is better to not give permission to edit templates to ALL users
only to some users who have special knowledge

2)
I run a test and created a new subdirectory under the main-theme-folder
files which have no php-extension are not loaded in the theme-editor.

So include-header.inc or _include-header.txt are not listed

3)
files with the extension "js / css / php" are listed

so you can rename the include-files as a first solution