The command versor-languide-convert-selection-to-variable takes the current selection as an expression, sets up a variable (at the nearest scoping point) initialised to that expression, and replaces the original expression with that variable.
The variable name is left on the kill ring, ready for you to re-use, as the likely use of this command is that you want to use a value in two places, where it originally occurred once, in-line.
In the normal Versor key bindings, this command is bound to C-insert =.
languide-make-variables-interactively is non-nil, the
users chooses the scope using an interface similar to
otherwise, it uses the following rules: