this has little to do with a TPO or VbP study, because, there is going to be single prints at the monthly high and at the monthly low, which would define the range.
So all you are really wanting is the high/low average for each month.
This can be achieved by using the "Period OHLC-Variable Period" study> Set the time period to months > Length to 1> Use current period: Yes. Then in the subgraphs tab change the "Draw style' of the "HL Avg" to "Line".
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