Managing variables in an external spreadsheet (excel) can solve a number of problems, especially as it is not easy to import variables into a Qlikview (Qvw) document.
It is difficult to set a variable containing a "macro expansion" e.g. $(=today()) without the macro expansion being evaluated as the variable is set. If the variable is stored in an Excel file it can be "imported" with some simple script into the Qlikview document as a variable.
You can create your own Library of Variables which you can import into a new Qlikview document.