Whenever you enter an expression, Ecolego will parse it to discover which objects are referenced and which functions are used. If you write the name of an object that does not exist, a window will appear that let you quickly create it.
The table has one row for each “unknown” object. In the second column of the table (“Type”) you can specify what type of object you want to create, for instance a parameter or an expression. You can specify the unit in the “Unit” field and also give a description of the object in the “Description” field.