Problem with mapping a key to multiple characters (Unicode + diacritic symbol)

[Pierre-Luc Angles]

Dear Ilya, dear ĸen, dear all,

Thanks for your messages.

The font that I am using with this keys is Junicode.

A big thank you to Ilya!!! In my terminal, I have entered
env XMODIFIERS='' GTK_IM_MODULE=xim libreoffice
LibreOffice opens and I can type all the compose keys that I have 
entered in ~/.XCompose !!!! I am very very glad! Thanks again Ilya!

Is there a way to automate this command or should I launch it every time 
I want to use these commands? Or is it "dangereous" somehow to have 
these commands configured like this all the time?

Best and thanks!!!

Pierre-Luc