Hello,
With Geany 1.23.1 using Tree Browser plugin version 0.20 in the left window, tree browser tab the right clic menu displays "Open Externally" This should be translated by "Ouvrir en dehors de Geany" Or maybe "Ouvrir dans un navigateur"
It depends what it does, really; as the expected command does not really work https://sourceforge.net/p/geany/bugs/1071/
++ Cyril