[horde] Share som IMAP folders

[Bzzzz]

Debian stretch
Horde pkgs V.5.2.17
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Hi list,

https://www.horde.org/apps/webmail says IMAP folder can be shared,  
however, I do not see any option to do so into 5.2.17, is it a feature  
for the latest Horde version only or am I missing something?

Jean-Yves