Add possibility to add parameters to external tools

Sometimes I need to add a dynamic parameter to an external tool, which cannot be specified by a variable.

Therefore, it would be nice to have a dialog prompting for this additional parameter(s), or adding them in the locator in the form

x tool <parameter list> 

Ice on the cake would be to have something like a wizard, which can also perform JavaScript operations, e.g. to fill a combo box where the user can select an item for the following operation. But having a simple input line would already be nice.