Here is the sample data-source
(My DS is not in order but I could see that sort in-order @ Tableau , but in any case you can arrange if it is not in order with the manual option )
STEP 2 : Make use of field Index() as Month-N
Now I can sort my actual Month with the help of INDEX field , I am sorting the same @ desc order (SEE BELOW)
Please set the answer as CORRECT & HELPFUL if it really helped you to sort your query so that it can help others as well.
This one-time option, and, if i will sort by this field next, it will sorted alphabetically again.
I would like to do task without unnecessary fields in my visualisation, but guess this is the only option.