Please see Japanese Keyboard Layout https://keyshorts.com/blogs/blog/37615873-how-to-identify-macbook-keyboard-localization#japanese .
With japanese keyboard '=' is typed by Shift--.
I looked at the inplementation of keyDown in SKPDFView.m.
} else if ([activeAnnotation isText] && (eventChar == '=') && ((modifiers & ~NSAlternateKeyMask) == NSControlKeyMask)) { [self doAutoSizeActiveNoteIgnoringWidth:(modifiers & NSAlternateKeyMask) != 0]; }
I checked eventChar variable is '=' when I type '=' by Shift-- with Japanese keyboard, but doAutoSizeActiveNoteIgnoringWidth doesn't call maybe because of ((modifiers & ~NSAlternateKeyMask) == NSControlKeyMask).
I did not realize this. Will be fixed for the next release.
Thanks!