As with scenario variables, block parameters need to have an initial value. This will be displayed in the value column. You can modify this initial value for each block instance's parameters by clicking on the value cell and typing in a new initial value. Alternatively you can double click on the value cell to edit the existing initial value.

Note that as with scenario variables, you are only allowed to supply an initial value that is compatible with the parameter's type and constraints (if any). If you specify an invalid value, the initial value will be reset to the default for that type.