Manifest Archive
My hard disk crashed.
All my DAZ content, on a different disk, was backed up, but I hadn't noticed that the Manifest Archive was in my Documents folder and was not backed up.
Can I recreate the Manifest without reinstalling all the Content? I have about 12000 items so that would be a major task

Comments
No, there isn't a way to scan the installed content and rebuild the instal manifests from that I am afraid. Be aware that if you do reinstal the content DIM will see that the files it is writing are already present and will make a not not to later uninstall them (on the assumption that they are shared files needed by something that was already installed) so you won't actually get much benefit from reinstaling. If you have the zips, or at least the package archives in the downloads folder, packages that chnage will be flagged - you can then decide how to handle reinstalling those particular products (e.g. rename the actual content directory, put an empty folder of the same name in its place, install the old package while working offline, then remove that dummy install, restore the name of the real folder, and run the update; or just manually remove the old files and instal through DIM).
Murphy's Law.
I'd spent a lot of time removing 3Delight options, to free a little bit of space, before deciding to get a bigger disk.Now that will, presumably reinstal. There might also be an issue with with mis-spelt folders I've corrected.
Does the Manifest affect the operation of anything except DIM? Can I just leave it and only download new purchases? (I suspect that would affect product updates)
3TB+ makes dummy directories a problem.
Your hard disk where the C drive located was physically damaged ? If it was not fully / physically damaged, you may still have chance to recover the manifest files with some recovery software ~~
And yes, manifest affects the info. of Installed, Ready to Download as well as product Updates.
My C drive is an SSD, but my Documents folders were on a separate D disk.. Professional opinion is that the disk cannot be started up for normal recovery. Most of it was backed up, but the Daz folder had not been flagged as vital.
Physical recovery would cost hundreds and, so far, I have only identified the Daz folder and my password list as missing operational files.
The C drive is OK, so the program appears to work fine, although DIM tells me the system files are not installed.
As well as the quantity of content, I have split definite Male & Female content out from G9, so DIM would see it as not installed. I have used the "delete after installation" option in DIM, so I only have about 1% of the total content which was files that did not delete, but appear to be installed.
Is there a way, such as dates, to identify Product Updates if the original files are still sitting in DIM apparently uninstalled?
Using Package Date and Order Date, I think I should be able to select new items and most Product Updates.
Might have to do a bit of tweaking, but I think I've picked up everything that wasn't already installed. It's just that my installed items show as 82 rather than 11800. I can't easily uninstall files if I run short of space, like I did before I got a new disk, but it should take me a while to fill 5Tb
I've now added the Manifest folder into the daily backup routine for my writing.