How to fix by yourself:
1. Use NotePad(support unicode) to open lua file.
2. Just change/modify "for i=0, #windowsList do" to "for i=1, #windowsList do" at line-11 and line-51.
3. Save lua file and refresh Rainlendar.
Thanks a lot for fast reply and the solution, this fix worked!
I don't know how many hours it would take me to find that kind of mistake in code. I wonder how many time it took for you to find that mistake in code?
Attached edited working script for interested people. It actually a very useful feature which is missing in original program. Devs should include this feature in the next version of the program!
It feels "OK and insignificant" when feature like this one is available but when it isn't there it is actually very uncomfortable to use the program.