I found this, but have never tried it.
Download your whole log from LoTW
If you need to download your entire log from LoTW as an emergency backup*, there are at least five options:
1. Use LoTW’s QSO reports to find out all you can about the missing QSOs and re-enter them manually into your logging program (tedious and error prone unless you are only missing a few QSOs);
2. Capture (‘screen-scrape’) the text one-screen-at-a-time from LoTW’s reports: this is also tedious and error prone, and is definitely not recommended;
3. Use the neat online LoTW log download utility by K1MU, without entering any specific QSO criteria;
4. Use this LoTW query page directly: it starts a full log download (thanks to G4LMW for the tip);
5. Use the ‘synchronise log with LoTW’ function in logging programs such as AClog (but not Logger32, unfortunately).
* This is a last resort: LoTW only stores the basic, minimal QSO details. Trust me, it is much better to make your own regular off-line and off-site log backups. Even if you only do a backup once a year, that at least gives you a fighting chance of retrieving your detailed log to a point within the past year, recovering minimal QSO details from then until now.