Yeah, I'm still using an old Logitech MX series mouse with sensitivity buttons I got with an Asus gaming laptop years ago XD. It's a brilliant feature.

Yup, i'm still using an 'antique' Logitech mouse with 2 buttons that r able 2 adjust DPI on the fly as well. Still works great & it's indeed a nifty feature. ;D That was a gd spot but that's also assuming 'they' were talking abt a game 'they' bought here. ;)

Idk what's with the quotes around 'they', but considering this is the GOG forum, i'd say it's a good assumption. Though the OP did make 1 post not mentioning the game in question at all and never replied. So who knows. I see these posts all the time though. OP makes a post complaining about something in the general forum, never even mentions what game they're referring to, and often doesn't even reply again.
I've had a few of the modern Logitech mice, including the G305 & G903 which i currently own. They both allow you to program up to 5 different DPI settings and store them on the mouse itself, so you don't need any 3rd party program after you set it up how you want the first time. They both also have buttons allowing you to cycle through the different DPI settings. One of them has 2 buttons for DPI, for going back and forth, the other has only 1. I think you can even have different colored lights for each DPI setting so you know without going back into a program what you're on. Though both of those mice are wireless so i just keep any lights off to conserve power.