1/ How to clear your Safari browsing history in macOS Sierra — You can remove all records that macOS Sierra’s Safari keeps of where you’ve browsed during a period of time you want. If your Mac and your other devices have Safari turned on to sync in iCloud preferences, your browsing history is removed from all of those devices.
Clearing your browsing history in Safari doesn’t clear any browsing histories kept independently by websites you visited. Choose History > Clear History, click the pop-up menu, then choose how far back you want your browsing history cleared.
When you clear your history, Safari removes all the data it saves as a result of your browsing, including the history of webpages you visited, the back and forward list for open webpages, Top Sites that aren’t marked as permanent, your frequently visited site list, recent searches, and more. You will need to log into services like Facebook again … so make sure you really want to remove all this data before you clear your Safari history.
2/ Bookmark folders — If you’re using Safari’s Favorites Bar (which can be revealed by choosing View > Show Favorites Bar from the program’s menus at the top), there are a few neat things you can do with folders full of bookmarks (Bookmarks menu, Add Bookmarks Folder). You can tell what bookmarks in the Favourites Bar are folders because of those tiny downward-caret-arrow things to the right of each one (above). Apple calls these Disclosure Triangles because clicking them always reveals things. If you click on one, you’ll note the Open in New Tabs option.
Choose that, and obviously the bookmarks within that folder will open in their own tabs, which is a fast way to launch a whole bunch of sites at once. If, however, you hold down the Option key on your keyboard before you click there, Open in New Tabs switches to Replace Tabs. This means any tabs you had in your existing Safari window will vanish and be replaced by the ones in the folder you chose. Neat!
3/ For an even faster way to do either of those things — Use the Command key or the Option key. If you hold down Command and click on any toolbar bookmarks folder, it’ll open the sites within in new tabs; hold down Option and click one, and Safari will replace your existing tabs like we just discussed.
4/ Set your folders to automatically replace existing ones with just a click — To configure that, right- or Control-click on the folder and pick Automatically Replace Tabs from the contextual menu.
That will add a little square next to the folder in your toolbar, which will mean a single click will replace all of your existing tabs with the ones in that folder. (Be careful about doing that accidentally. If that happens, there are ways to recover your lost tabs.)
5/ Some of this functionality is available from the bookmarks sidebar if you prefer that view — For example, you can right- or Control-click on folders from there to pick Open in New Tabs. Holding down the Option key will switch that to Replace Tabs, as it does in the toolbar. [These last four tips came from The Mac Observer, which has more pictures.]