Canvas - Action Button - Need Expression for set value and write value features

Currently I have to add calculations to a cell in the spreadsheet, I need to name it (Named range) and can then in Canvas I can add the named range.
I want to directly add the Expression (Calculation) to the Action.
View Screenshots. The screenshot with "Button_Expression" shows the Expression selection. This is needed for set value and write value.
This can be an simple Expression as: add text of variable 1 and variable 2.