You can try to change the text size in the Display Settings control panel. Hit the Windows key, then type "Display settings" and select the control panel with that name. I have it set to 100% and then the Modeler looks fine. See the attached image.
Since the update to MX 6.2 I had some trouble too, I'm running on Windows 8.1 with a 4 k resolution but what I did was enabling the compatibility option: "Disable display scaling on high DPI settings", which helped for me since setting the display setting: "Change the size of text, apps, and other items" option like Arjan suggested resulted in tiny text on all other applications other then Mendix. I think it would be great if we get some kind of setting in MX instead of having to deal with this via compatibility settings or the overall Windows scale.
To get to the compatibility settings, right click the icon in your taskbar/start menu/desktop for the taskbar then choose the program and click properties for start menu/desktop click properties then go to the compatibility tab.
Looks like this is also not working with Windows 10. If you observe there is an option "Run this program in compatibility mode for" Under this there is no option for Windows 10. I think we should have windows 10 option added here.
I had the same issue on my laptop, restarting the laptop fixed this for me.
I had this same issue with my old laptop. Is your laptop touch screen? I fixed the issue to changing the resolution down to 1920 x 1080p