You may specify any string instead of an operand if IDA does not represent the operand in the desired form. In this case, IDA will simply display the specified string in the instruction instead of the default operand.
The current operand (under the cursor) will be affected.
You can use this command not only with instructions but with data items too.
IDA proposes the previous manual operand as the default value in the input form.
To delete the manual operand and revert back to the default text, specify an empty string.
IDA automatically deletes manually entered operands when you change operand representation using operand types submenu.
NOTE: A text offset reference is generated if you use a label in the program as the operand string. In other cases no cross-references are generated.
See also Edit|Operand types submenu.