I make this quick and dirty modification to be able to use OR in filter because I do not know how to make a plugin. I hope someone will make this into a plugin 
It is for redmine 2.3.2 so I do not know if it works for other version. 

A. How to install
1. Install (copy to plugins folder, no need for migration) redmine_involvement_filter (modded version, included here). The author of this plugin is Alex Shulgin <ash@commandprompt.com>. I "borrow" and modify it to include a filter to mark for using OR
2. Either replace the whole query.rb in /$redmine installdir$/app/models with the version included here, or you can edit the query.rb manually and replace the def statement block with the version I include here
3. Restart redmine, that is all

B. How to use
- The project filter is alway AND regardless where it occurs
- For others, please add the filters to be AND first
- Then add Start Or filters
- Then add the filters to be OR

C. Example 

status is active
start or filter
assignee is me
watcher is me
author is Ms My Lover

Then the effective filter clause will be 

status is active AND (assignee is me OR watcher is me OR author is Ms My Lover)
