All Supported Smarts releases
While it is not explicitly mentioned in the interface or documentation, there is an implicit assumption that all values are single lined. Values that contain more than one line are not accepted while importing.
You can see entries related to this in the following log file for example for the setting Ethernet_Performance_Setting.
[<Date & Time>] t@<EPOCH> SM_ProtocolEngine-10 6624 Perl-Client-6624-1
ASL_MSG-*-ASLP-icf/init-settings.asl: Setting 'Ethernet_Performance_Setting' defined outside of configuration.
When values with multiple lines are present, only the first line is taken and everything after that gets discarded. That is why you only see the first line in the description field once it is loaded. This happens because within a configuration setting definition, no empty/invalid lines are permitted. Since the multiple-line description causes the extra lines to be discarded, the configuration setting definition is assumed to be ended there.
The Smarts sm_settings.pl settings import script is working as designed.
One possible future Smarts IP enhancement is to strip off extra lines (or replace new lines with space) during export to ensure the resulting file can be safely imported.
Please open a product enhancement request if you desire this functionality.