You want to sell all shares at once without entering the decimal places?
Then install at least the app update 2.43.1 and the option is automatically available.
To use the button, you can proceed as follows:
Go to the desired portfolio
Now select "New transaction
Select "Sell" for the type of transaction
Now select the security or the position
In the next step you can simply click on "Sell all".
Finally just "Add transaction