i've a problem, i'm able to search for string in messages.app. It actually tells me all the matches for every conversation, the problem is that is shows only the last match, how can i go through all the results?
You can simply use
- ⌘ + G in order to jump to the next occurrence
- ⌘ + Shift + G in order to jump to the previous one.
Have you tried Spotlight Search?
Cmnd + Space
Make sure Messages is enabled for Spotlight Search in your Mac System Preferences.