You can copy and paste keys from one calculator to another to create your own custom calculators.
You should first create a calculator instead of modifying a calculator that ships with CALC 1.
This is very easy. From the Calculators list, tap the edit button, then the add button. CALC 1 then creates a copy of the calculator at the top of the calculator list. So before you create a new calculator, reorder the list to place the calculator you want as a starting point at the top of the list.
You can also Enable the "Key Editing From Calculators" option to display the key editor directly from the calculator.
Then from the Key Editor, tap the copy icon. Navigate to the target Key then tap the paste icon.
If you paste or delete by mistake, use the shake gesture or tap the undo icon to undo.