In a normal zoom, the out arrow is not clickable, because it is too small, and the mouse cursor becomes tiny hand (like 25% of my normal cursor size, which 2 in Window’s Mouse pointer settings). I think it is probably because it is not handling high-DPI well. Notepad is for size comparison.
If I zoom in more, I could click the single-pixel-like with an utmost precision and care and trials. This is the minimum zoom level I succeeded.
This is the zoom level, in which I can relatively easily click the out arrow.
Seems like this application is using QT4 and has problems with high-DPI, until it is upgraded to QT5. Meanwhile, is there a way to connect two nodes in a smaller zoom? Like some sort of modifier+drag?