Reading .flo files

I'm pretty new at Arduino. Maybe a month. Retired HW Eng looking for for some coding fun for a change.

I'm using Windows 10 and I use my own old VISIO prof. 2003 to make my own flow diagrams when the code gets big.

I'm making a Juke Box for my grandson and it's loads of fun. Some of the code is repetitive. It seems IDE doesn't have 'subroutines', so I'm wondering what to do. Reading examples offer functions and forks. These reading examples explaining what I should do are offered using ".flo" files. I presume these are flow charts? I cannot find a recommended free app to read these files.

So my question is 2 fold:
1 what is a good easy free flow chart reader?
2 could you point me in a good direction on how to reduce repetitive code?

Thanks All

In this world You use “functions”. They work the same way.
Have a look here: Arduino Reference - Arduino Reference

Can you post your code as it is now and point out specific problems you’re trying to solve or optimize?