After much searching, I managed to find my saves in the Content Manager, but only under "Online Storage" (PS+). The heading for
PS Vita System → Online Storage is "Saved Data (PS Vita)".
PS Vita System → PC, the only "Saved Data" options are "PSP/Other" and "PlayStation" (no "Saved Data (PS Vita)" option).
Is this because PS+ online backups override this setting? Do I need to disconnect my PSN account in order to move the saves to my computer? Or is this setting not normally available in the PC menu anyway? How can I back up these saves?