Editing first post

I wish that in some forums I would be able to always edit the first post in a thread if I had created that thread.
I want this especially if the thread is about an item that get continuous updates. If there are more news, I would like to update the first post with the updates.

Right now, you would need to be a moderator or an administrator to be able to do that -- and there are moderators and administrators that do maintain such threads.
But how about threads created by regular members?

One example: CEII ROTJ and AOTC-3D movie screenings. I would like to edit the first post to contain more accurate information about where and when the movies are going to be screened.

 

The first post is indistinguishable from any other post with regards to editing ability. Unfortunately, what that means is that in sections without unlimited editing, there's no way to implement your suggestion. What you can do is PM the relevant forum's moderator(s) asking them to edit the post for you.