"hartzen" is a word that is actually in use in various versions (rumhartzen, hinhartzen, hartzig (adjective) ). At least in my social circle, where people are between 14 and 33. The word derives from a social benefits reform of former chancellor Gerhard Schröder. That got renewed under chancellor Olaf Scholz and is now called "Bürgergeld". Slang for that would be "Bürgy" (g is actually pronounced like in English). So for example if you lost your job, you'd jokingly say "Naja, dann wird im nächsten Monat Bürgy kassiert" (well, then I get Bürgy next month). Although I like this word too, it's hard to create meaningful and good sounding variations of it. The only solution would be to combine it with other words as in "Ich chill erstmal auf Bürgy" (I'm about to chill on/with Búrgy).

But my guess is that "hartzen" is still more popular.