I presume you are saying that this "earliest version" does not have the bookmarks you want.

You can restore deleted bookmarks from iCloud.com, although it is rather messy:

• Browse to http://iCloud.com.
• Click on Settings.
• In the lower left corner, click the link Restore Bookmarks.

It is somewhat buggy, but if you only need to use it a few times in your life, while travelling, it is tolerable.

If your bookmarks have been upgraded to Apple's newer CloudKit system, which is probably true unless you still have an Apple device running a OS older than 2013 or so signed in to iCloud, you will see a list of your recently-deleted bookmarks.  There are supposed to be checkboxes in the left column.  The idea is you switch on the checkboxes of bookmarks you want to restore.  But they checkboxes may be invisible.  Click around until one of them lights up.  Or, try "select all", which may not be what you want, so then you must un-check the ones you don't want.

If you see a list of dates instead of a list of bookmarks, that means you're still on Apple's old system.  Choose a date, Restore, wait for it to indicate completion, look at your bookmarks in Safari, and if you don't like what you got, repeat with a different date.

Hello, schnaxxl.  Try the Third Method on that support page which explains how to restore bookmarks.  If you did import Safari bookmarks when you first created your new Collection, it should have immediately saved that version with Safari bookmarks as they were, and that version should be available in the macOS Versions Browser.  Click all the way back to the first available version, then restore.

If you don't find them there, do you have a Time Machine backup of your Home Folder?  If so, go back and get yesterday's version of ~/Library/Safari/Bookmarks.plist but do not just Replace the current version because that will cause iCloud to go bonkers.  Import into BookMacster instead – I can tell you how to do that.

Do not switch on Syncing until bookmarks look good in BookMacster, Safari and any other browsers.