When you go to update a calculation for an field you need to click the gear icon and then scroll down to or search for the assigned expression before you can begin to edit it. In smart forms that have lots of calculations, this can be quite tedious and adds an unnecessary level of friction to updating existing calculations.
There should be an option to edit the existing expression right from the calculated expression part of the side panel, or at the very least pin the existing expression to the top of the list when opening the calculated expressions list pop-up. That way you do not need to go hunting for the expression that is already connected to the field. We should not need to click the gear icon then scroll through a big list or type in the name to find the expression, I can see the name of the expression assigned right there, why can I not just click and edit it?
Examples:

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