It was pretty easy to manage Bookmarks in MobileMe. When I wanted to update all my i-devices with the latest Bookmarks from my main Mac, all I had to do was use the advanced features in sync to replace everything in MobileMe with the data on my main Mac. But I can't find how to do it with iCloud. After syncing everything with iCloud today, I find that my Bookmarks Bar has been merged with older versions on all my Apple devices, much to my displeasure. I'd like to use the current one on my main Mac, which I had to retrieve using Time Machine. How can I force iCloud to erase all my Bookmarks data and replace it with the Bookmarks from my main Mac?
Thanks for the response, which gave me enough of a hint to let me answer my own question.
I've now got the Bookmarks Bar that I want on all my iCloud Apple devices. Here's how I did it:
1) Launched Safari 5.1.1 on my 10.7.2 iMac and navigated to Bookmarks>Show All Bookmarks.
2) Made sure the Bookmarks Bar under the Collections heading was exactly what I wanted it to be. Noticed there were two other Bookmarks Bar folders under the Bookmarks heading (no idea how they got there), and that they contained different versions of very old Bookmarks Bars, which was the source of the corruption of the Collections Bookmark Bar that had been synced to iCloud.
3) I deleted the two Bookmarks Bars under the Bookmarks heading.
4) I used TinkerTool to make the Library folder in my home Users account visible (Lion hides it) so that I could make a copy of the Users>(home folder)>Safari folder. I put that copy on the desktop.
5) Next, I went back to Safari>Bookmarks>Show All Bookmarks>Collections>Bookmarks Bar, then highlighted and deleted the entire contents of that folder. All bookmarks in the Bookmarks Bar disappeared.
6) After about 10 minutes, or a long enough period of time for the new Bookmarks Bar to sync with iCloud, I went to my iPad 2. I previously had used Settings>iCloud to turn off Bookmarks syncing, which action gave me a selection of choices. I chose to delete all Bookmarks from my iPad 2. This time, I turned on Bookmarks syncing. After a few minutes, I went to the iPad's Safari and saw that the blank Bookmarks Bar indeed had replaced the old one.
7) Back to my iMac, where I closed Safari, then copied the saved "good" copy of my "correct" Safari user folder on the desktop and chose to have it replace the Users>(home folder)>Safari folder.
8) I launched Safari again to find the correct Bookmarks Bar had reappeared. After waiting for 10 minutes again for it to be synced with iCloud, I then went to my iPad 2 and found that iCloud had synced the correct version of my Bookmarks Bar.
Problem solved! The key piece of information is that a Mac running OS X 10.7.2 and Safari 5.1.1 is necessary to force an iCloud data flush. Lord only knows how an iOS-only user is going to do what I did. Another vital piece of information is that a third-party utility such as TinkerTool is needed in order to unhide the hidden Library folder in the user's home folder on a Mac running Lion. And Apple decided users didn't need to see and access that folder!