Syncing the templates between users/machines is kind of tedious work and requires some caution.
Different from clips effects can't be relinked and so there is some potential for risk.
There are 2 places where templates are stored:
(Note "~" stands for the current user)
The FCP X way
The "classic" way
/Library/Application Support/Final Cut Pro/Templates/theType/someFolders
If you modify or create a Motion template it will be stored by default at ~/Movies/Motion Templates/theType/someFolders. That's fine in many cases since many FCP X users are a one man show.
Having more than 1 user working on the same project will make it more difficult – even if they work on the same machine. The template is only available for the user who created it.
Here comes the second location option. If the template is stored in /Library/... it is available for all users.
If it is planned to work with different users/machines – even if not – the template should be saved. Applying a theme there is also recommend. Don't use it directly in the project you are working on. Instead navigate to the template in Finder and move it to the matching place in /Library/... then relaunch FCP X.
Commercial templates (free or paid) often come with their own installer. Some require a host app like fcFactory. The location where they are installed differs. Some use the user location some the global location. In any or most cases the user has no option to select where the template is installed.
If the template is installed at user level it's the same dilemma as above.
With fxFactory based templates the (other) user can launch fxFactory and install the missing template.
With other template installers the (other) user must run the installer again.
Some people share their projects via XML. I don't recommend that cause several parameters will be ignored when creating the XML and some of the left ones will be ignored during import. For simple stuff though XML is highly effective.
But there is one thing where XML can help a real lot: template syncing.
You can create a XML. All assets and effects will be listed in the "resource" part of the XML. So you can open the XML in TextWrangler (or something similar) and find the "effect" entries and their paths (uids) manually. This is both time consuming, boring and not effective.
That's why I made my X-FX Handler some time ago.
It will use the XML to find all FX and tell you whether the FX is found for the current user or not.
The second option is to create a report about the external FX used.
So if a user wants to share a library with other user or move it to another machine he can create an XML upfront to create a report of the original state.
Moving/sharing to another place and creating a new report from the original XML.
This way missing paths can be retrieved easily – and hopefully be fixed.
There is a bit more detailed description about reports at www.spherico.com/filmtools/X-Files/X-FXHandler/XFX.pdf
Fixing the paths though can cause duplicates of the effect if it already exists somewhere. If you are sure that a missing effect (found at a different location) was never used on any other project on this machine you can move it otherwise copy it. In case it not found you need to install it.
Some more notes about Motion templates.
While you can (and should) assign themes some things are mostly forgotten.
If you create a template you also should enter something into the "description" field especially when changing something. It's not visible in FCP X but can help a lot using Spotlight to keep track of templates.
Another thing which unfortunately is not directly accessible in Motion is the "build". Therefore it won't be saved or better left empty. You can change that manually in the XML.
Changing those things won't destroy any links.
With installer applications like fxFactory the file paths displayed in Finder look different from the "displayed" paths.
Each template has it's own unique ID – means vendor/type/name etc.
This can lead to some confusion when you are searching for a missing FX.
Here an example what's stored in the XML:
This is obviously not very helpful at the first glimpse. It links to the wrong directory and also displays a not human readable path to make sense.
Resolving the path (in case it is found) will result in:
~/Movies/Motion Templates.localized/Effects.localized/Sheffield Softworks.localized/Makeup Artist.localized
This looks more usable and can be used with "find" to check whether the FX can be found somewhere else.
BUT finally both paths are WRONG. None of them do exist!
(Note "~" stands for the current user)
The first one points to the wrong directory: "~/Effects.localized" instead of "~/Movies/Motion Templates.localized/Effects.localized".
So FCP X does have it's own special UNIX paths aside from normal standard.
The second one points to the right directory, but the rest of the path is wrong:
"Sheffield Softworks.localized/Makeup Artist.localized" doesn't exist in the file system only in the Finder system that's why it can be found by Spotlight's search function.
The real path is "~/Movies/Motion Templates.localized/Effects.localized/0A85C409-34EF-433A-84D4-DCC185550BFF.localized/57417529-5011-48E9-8B0F-660EFCC1EF82.localized/"
Hope this helps to understand a little of the underlying stuff with templates.
Here some graphic to show how things are (can be) related.
Themes can be used across template types. This will make sense if you have a special type of projects which always use the same set of templates (independent from template type).
If you have a lot of "home made" templates you also can use the same category for all of them.