[swiiscompos]

No, when you input the target tempo the script will automatically calculate the number of bars, including the shorter bar if the option is on an then it will output the result as text (for example "12 x 4/4 + 1 x 3/4, tempo: 120.83", like on the mockup). At this point you can simply hit "Apply".

Now imagine that your target tempo was 120. Maybe you prefer to have a 2/4 rather than 3/4 and in this case you can simply click the "-1 beat" button to get a preview of what the new tempo would be. If you don't want to use the buttons, you don't have to, the script will still run correctly.

Also you hit "Apply" only at the very end of the process, that's why you have a text output, to let you preview the created bars before you hit "apply".

The script has been created so that each time an option/input is modified you simply have to run the whole script once.

EDIT:
So basically you can just enter a target tempo and hit apply. It will create a new bars, all 4/4 time signature.

Or you can enable the creation of a short bar, position it at the end, enter a target tempo, decide you are not totally happy with the result, use the +1/-1 beat buttons to see how far another time signature would be from your target tempo, and finally hit apply when you are satisfied.