At this time, that is not possible without some customized web service to look up the old interaction and create a new outbound one (if the service supports it like WhatsApp). There will be a future feature that allows agents to reply to closed interactions, but not sure if this will include social media. @Atsushi Hirano is that in your purview?
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Robert Wakefield-Carl
ttec Digital
Sr. Director - Innovation Architects
Robert.WC@ttecdigital.comhttps://www.ttecDigital.comhttps://RobertWC.Blogspot.com------------------------------