My new laptop has a 4K monitor and my tool of choice for writing my Arduino books, Lyx, always displayed the toolbar icons as “so very tiny, it is hard to see the damned things!” After much experimenting with the monitor’s scaling, fractional scaling and such like, I found QT_AUTO_SCREEN_SCALE_FACTOR which should fix things. I tested: 1 2 export QT_AUTO_SCREEN_SCALE_FACTOR=1 lyx & and yes, the icons were now usable. Hooray. I just need to make this permanent.