Ask HN: 20s COBOL Dev with an itch to scratch

So I got a job as a COBOL dev that I accepted for financial reasons just before actually getting into the software development part of my engineering studies. I am very happy staring at green on black all day but I really miss having the know-how to build something useful for myself in my spare time.

I grew up with C64s and C128s harvested from local flea markets and bought a Windows desktop in high school. While looking at what to dive into I feel like I should learn a ton of C (used at work) or Java (migration work in the future?) but I would really like to learn something that I can build my own windows programs in (windows managers, file handlers, automating tasks come to mind), nicely packaged and maybe to put some of the good stuff on git for others to try.

I really feel a bit lost looking at modern languages and the pros and cons of them, so what should I do? Is C++ the way? Java reminds me of the hoards of sluggish EVE-Online repackaged spreadsheets and .jar files but maybe I just don't know what desktop apps are made in. I would really love some input from the hacker news-readers.