You can use a variable that represents the default value of that text input, which you can initialize to 0 (such as on the screen's OnVisible property) - and you can also use a button to set that value back to zero, resetting the value.
Screen.OnVisible: UpdateContext({ value: 0 })
SummaTextInput.Default: value
ResetButton.OnSelect: UpdateContext({ value: 0 })On the list of items, I'm assuming you have them in a gallery. If the value (in krona) is represented by the column 'Value', then you can have this formula in the Lägg till button:
LaggTillButton.OnSelect: UpdateContext({ value: value + ThisItem.Value })That will update the 'value' variable, and its value will be reflected on the text input.
