install Thunderbird extension (addon) globally

I have downloaded a Thunderbird extension as a.xpi file.

I know, I can install it in Thunderbird by going to

Tools
  -> Addons
     -> Install Add-on from file

However, I am using several Thunderbird profiles and I would have to do tis for each of them.

How can I install this addon globally (presumably somewhere in/usr/share/xul-ext) ? Do I have to unpack this.xpi` extension file there ?

I can install it in Thunderbird