Write Expression values back to OPC Item

Hi
I would like to add an expression to a tag in Ignition, and to that I would like write the calculated value from the expression back to the OPC item. In the link below there is described on how to do. But I can’t find the check box. I think my Ignition is 8.0.
Does anyone know how I can fix it?

Creating Expression Tags - Ignition User Manual 7.8 - Ignition Documentation (inductiveautomation.com)

You should upgrade, 8.0 is not a version you want to be using - I don’t think it’s supported anymore.
And then, you should use the doc related to the version you’re using, there’s a huge gap between 7.x and 8.x.

I think you’ll have to use a derived tag, which can hold a read expression and a write expression. Those expressions are used to ‘transform’ a value from and to another tag.
https://docs.inductiveautomation.com/display/DOC81/Types+of+Tags