In the menu bar -> Insert -> Fields -> "More Fields..." -> Variables it is possible to set variables by filling the "Name" and "Value" fields and clicking on "Insert". But I'm wondering why variables must be inserted to take effect. Normally I would expect to only set them without inserting them in the document. Maybe there could be also a button that does only set variables without inserting them. Or maybe the "Invisible" checkbox could be changed to do this (as currently it just hides the variable while still inserting it which is visible with a gray background).