@djuntgen: http://www.mantisbt.org/development.php which should get you to http://www.mantisforge.org/dev/manual/master/en/developers.html

I didn't try myself
Description is: Show history entries inline with bugnotes.
http://git.mantisforge.org/w/inline-history.git

Please close ticket, plugin does exactly what is needed.

I think this issue should not be closed.
IMO the most wanted plugins with a good quality should become part of standard MantisBT delivery.
If not, users will install various plugins and after upgrading core of MantisBT they might find, that there are problems with plugins.
This can't be avoided all time, but at least for the most wanted plugins should be.

I do like the inline notes / history...however and issues that have a lot of history and notes, it becomes very busy and hard to follow. Cool tip - There is a setting within the user preferences to turn on/off the inline history/notes.

So - I'm not sure how you would go about getting a plugin within the standard distribution but another one I know I would love to see more support for is the GIT Source integration.

As part of the modern UI work, we should consider the streamlining of the View Issue page. I believe having some header information then chronological actions like notes, attached issues, history, etc.

For the record, new address of the inline-history plugin
https://github.com/mantisbt-plugins/inline-history