thanks for your feedback and contributions.

Just a short addition for those who want to use more buttons (via the 
Harmony) with Plex, but feel that the Apple Remote is sufficient for 
all other apps. Here's all that needs to be done:

1) Go to Remote Buddy > Prefs > Mapping > Plex 
2) Map all buttons of the Apple Remote to their respective equivalents 
of the Virtual Remote. Including the Menu and Menu(hold) buttons. (=> 
12 clicks at most)

Support for multiple remotes does not need to be enabled for the 
forwarding of Apple Remote IDs to work.

Regarding direct support for the Plex Harmony Setup: 
I do not intend to add direct support for the Plex Harmony setup, 
because it appears incomplete (f.ex. the record button doesn't seem to 
have any Apple Remote code mapped to it) and too Plex-specific to me. 
If a special Harmony mode is going to be supported, it has to be 
general purpose, include all buttons and should ideally not rely on 
third party profiles. I'll see what can be done there. If you have a 
contact at Logitech with the ability to add new profiles to the 
Harmony database, this would certainly be a great (and appreciated) 
help. I'll not make any promises at that point, though and kindly ask 
that the obvious and understandable (but to me really just greatly 
annoying) questions of "when?", "is there a timetable?", "in which 
release?" etc. are not going to be asked.

Regarding sharing of settings: 
Sure, that's very easy. All settings for a particular remote are 
stored in a file of its own (to make sharing easy) and saved at

~/Library/Preferences/com.iospirit.remotebuddy.com.apple.builtinir.plist 
~/Library/Preferences/ 
com.iospirit.remotebuddy.com.apple.remote.<unique ID>.plist

Ideally, if you want to put together a general purpose settings pack 
for others to use, you wouldn't make use of the default, logical 
remote called "Apple Remote" at all, because that's where the settings 
for the normal (non-multi-remote) mode are stored, too and users may 
already have adapted settings there.

One last, general comment about copying/replacing/adding preference 
files that applies to all apps: 
They should only be worked with when Remote Buddy is not running. Why? 
Because the OS X preference system usually just caches changes and 
saves them only when an application quits - which might then overwrite 
manually changed preferences files with what the OS X preference 
system previously had in memory.

Best regards, 
Felix Schwarz