I just learned that there is a new command “Toggle completed” (Ctrl-Enter) in 0.9.5 that can be used here: You can mark the whole checklist (Ctrl-A) or parts of the checklist and then press Ctrl-Enter. However, this does not achieve our goal with a partially completed checklist since it toggles all checkboxes, it does not (re)set them. It also only works in edit mode. A “check/uncheck all” command would also make sense in preview mode.