I'm running KDE Plasma desktop in Arch Linux.

In GTK-based applications, when I use the Ctrl-arrow shortcut to move a text cursor around words, it stops on underscore characters. e.g. If I am in a "Save File" dialog in GTK and my cursor is at the end of this_character_sequence, pressing Ctrl-<Left> will move the cursor to the left of the s in sequence.

In KDE (for example, Dolphin or any KDE save file dialog), doing the same thing would move the cursor to the very beginning of the sequence, as the _ is not interpreted as a break between words.

Is this behavior configurable anywhere? I would like my KDE applications to interpret the _ character as a word break. I've looked around the (extensive) KDE settings, and cannot find anything related.

I don't think you can, an underscore is defined to bind words, the hyphen is the one separating words. At least that is how shortcuts are working in Plasma.

If you think this is wrong, file a bug at https://bugs.kde.org