very small IDE at screen resulution 3860x2160

[BlindDuck]

any text unreadable, while the symbols are easy to miss.

[PaulStoffregen]

Squint and use File > Preferences to change the scale.

[BlindDuck]

changed to 400%
OS: openSuSE TW
result:

only the window title and IDE font are enlarged

things not getting better, unfortunately

[BlindDuck]

However under Windows 10 scaling of the whole IDE is possible!

The following pictures are made with 250% Scaling of Windows and 100%/automatic of the IED:

And with 225% Scaling in Windows and 400% of the IED:

[stapelberg]

As a shot into the dark: check your gtk-font-name value. I had gtk-font-name "Bitstream Vera Sans 8" in my ~/.gtkrc-2.0. Changing font size from 8 to 12 worked for me.