My suggestions are rooted from core Splunk functionality first rather than adding it externally.
First thing you can try is adding some functionality in your search that orders the values accordingly. Using commands like
eval may help with adding logic and the flexibility to output your desired field name/ values. Here is a simple example using
date_wday that you could use for your Month - Year values (To test, I looked at the Previous Week using the Time Range Picker in my local dev instance):
index=_internal | stats count by date_wday | eval week_day = case(date_wday="sunday","0",date_wday="monday", "1", date_wday="tuesday", "2", date_wday="wednesday", "3", date_wday="thursday", "4", date_wday="friday", "5", date_wday="saturday", "6") | sort week_day | fields date_wday'
Another option might be to use a lookup file in your search to output field name/ values you want. The first column header would be the original field name with its list of values, and the second header would be your output field.
Let me know if this is heading towards the right direction or not we'll go from there. When in doubt I recommend using Splunk first before JS, etc.