I want to use a term to covers both creating and editing some entity, say a blog post or a comment in a blog. Which word should I use?
The verb form of author encompasses both creating and editing a work of some kind.
Jill authored her personal web site using Fireworks.
I think the word producing (or production) could cover both writing and editing.
Produce has these definitions:
Whereas you are referencing blog posts I would use the phrase WIP for Work In Progress. That phrase also has a connotation of Superordinating; that is to say it's similar to a Hyponym. Also Rudimentary or Rough-Hewn or Unfledged; there are several others as well, all of which establish that you are in the process of creating and perfecting. Hope this helps.
I am used to Drupal world (which calls posts, comments, and users entities) where, when I create an entity, I am immediately asked for the values to give to the fields associated to the entity (e.g. the title, the body, and the timestamp of a post; the title and the body of a comment). Create is the term used in that case.