The ODBC entries can be backed up and restored from the registry entries.
The ODBC entries are present at the following location:
HKEY_CURRENT_USER\Software\ODBC for User DSNs
HKEY_LOCAL_MACHINE\Software\ODBC for System DSNs
and File DSNs are stored in directories. These directories are listed in
KHKEY_LOCAL_MACHINE\Software\ODBC\ODBC.INI\ODBC File DSN
So you can go the these entries, right click and click export. All the DSN will be exported to a file.
To restore simply go the File menu of Regedit and click import, choose the previously exported file and thats it.
About the second part of your question:
SQL-Assistant stores the customized information in XML files at the following path:
"C:\Users\<username>\AppData\Roaming\Teradata\SQL Assistant" on Win-7
OR "\Documents and Settings\<username>\Application Data\Teradata\SQL Assistant" otherwise
The files are as follows:
DataSources.config -> contains all the odbc sources defined through SQL-Assitant define data sources option in Tools menu.
DBTree.config -> Contains all the customizations for the databases added to the DBTree.
Toolbars.config -> Contains all the customization made to Toolbars
UserOptions.config -> Contains all the customizations to useroptions.
Hope now you will be able to backup and resotre your whole SQL-Assistant customizations.