Shortcut: <Ctrl>+<U>
This command inserts an operator input. With many operators, the number of inputs may vary. (For example, ADD can have 2 or more inputs.)
In order to extend such an operator by an input, you need to select the input in front of which you wish to insert an additional input (Cursor Position 1); or you must select the operator itself (Cursor Position 3), if a lowest input is to be inserted.
The inserted input is allocated with the text "???". This text must be clicked and changed into the desired constant or variable. For this you can also use the input assistant. For the possibility to enter an address instead of the variable name please see the description of the options dialog.