MAXQDA Stats offers an easy possibility to combine the items 
shown in the result table in a scale and save it as a new variable. Click on the 
symbol Build scale and save as new variable  to start the calculation. A dialog will appear, in 
which you can enter a variable name and a variable label, and set the kind of 
calculation.
 to start the calculation. A dialog will appear, in 
which you can enter a variable name and a variable label, and set the kind of 
calculation.

Define variable name, variable label, and the kind of calculation for the new variable
Summation – The sum of all single item values will be calculated for a case.
Mean – The arithmetic mean of all single item values will be calculated for a case.
If a value is missing for an item or the value is defined as a missing value, the newly created variable contains a (system defined) missing value for the respective case.