https://twinery.org/questions/49770/prompt-macro-broken?show=49770#q49770
https://github.com/klembot/twinejs/issues/545
https://github.com/electron/electron/issues/472
For a temporary workaround, if anyone else wishes to fix this on their end, for v 0.23.2 (iirc?) adding the text "return;" to the end of line 1801 should fix the problem. I've made this change on my save and am able to use save slots normally.