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I'm not aware of a way to do it on launch, but if you have all of the sites you want to open in tabs in a folder on your Bookmark Bar, you can just immediately select that folder and choose "Open in Tabs." You can also investigate the "Auto-Click" function in the Bookmarks window...that'll automatically give you the sites in the specified folder with a single click.
 
i do not believe this is possible

you could possibly try downloadin all the various plug ins for safari (ie: saft, safaristand) and then fidget around and try to make it work? but i dont recall seeing anything of the sort in any options menus on any safari browser or plugin/extension, etc

sorry
 
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