Theo đây (https://mail.gnome.org/archives/evolution-list/2008-November/msg00098.html) thì:
Hi,
when staying in a tree, press Shift+Left/Shift+Right, I think it's a
standard shortcut for such action in Gtk+, but I'm not sure.
Hope that helps,
Milan
Thank you Milan
Ctrl + H để select nguyên thread và Ctrl + K để mark nguyên đống đó as read.