Finder is used to navigate your Mac's drives, iCloud, and other storage locations. Customizing the app to show exactly what you need can make you far more productive.
Drag and Drop Makes This Easy
As is the case with many aspects of the macOS operating system, drag and drop is your friend. To add a location to your Finder sidebar, you can simply navigate to the enclosing folder and then drag the folder into the relevant section to the left. You can also the folder you have open by clicking and dragging its name at the top of the window.
The "Favorites" section can hold anything: local drives, cloud storage locations, external disks, remote computers, optical drives, whatever you like. You can also drag other locations to the relevant locations, like folders stored in iCloud to the "iCloud Drive" section for example.
Furthermore, you can remove items easily this way too. Simply drag a location out of the sidebar and then release when you see the "X" appear. Alternatively, right-click (Control+click) the item and then use the "Remove from Sidebar" button to delete it.
Lastly, don't overlook the order in which your items appear. Use the same drag and drop technique to reorder your favorite locations, in any section.
A properly organized sidebar can help you find and triage files quickly. You can drag files and folders onto your sidebar shortcuts to quickly move or copy the contents. Most of us are creatures of habit, so having a visual shortcut to get places is easier than using Finder shortcuts like Command+Shift+G to bring up the "Go" box.
Toggle Locations via Finder Sidebar Settings
Dragging and dropping is the easiest and fastest way to organize your Finder sidebar, but it's not your only option. Open a new Finder window then click Finder > Settings > Sidebar at the top of the screen to see a full list of locations that you can toggle on and off.
Though it's quicker to add regular folders with a drag and drop, finding more obscure locations can be a hassle. You can use this settings panel to add locations you might have removed, like the "iCloud Drive" root directory, "CDs, DVDs, and iOS Devices" locations, "Shared" folders, and "Connected servers" on remote machines. You can also turn tags on and off from this menu.
Remember that you don't have to remove items altogether to hide them. You can collapse a section (like "Tags") using the arrow that appears when you hover the "Tags" section heading.
Don't Forget About Tags
Tags might be the best Finder feature you're not using. By using tags, you can color-code your files to help prioritize, organize, and separate whatever it is you're working on. Tags appear in your sidebar, beneath your other useful locations.
Open a new Finder window then click on Finder > Settings > Tags to customize your tags. Use the checkboxes to enable or disable tags as you see fit. Right-click on a tag in this window to rename it, or reassign the associated color. You can also delete tags this way.
The tags you enable are just those that will be displayed in Finder's sidebar. You can turn tags off and still have access to them under the right-click menu. It might be best to keep just a small selection of tags associated with files you need to recall frequently, rather than leaving everything enabled.
Customizing the Finder sidebar can make you more productive. You should also consider enabling the path bar (and path icon) in Finder and creating some useful smart folders (saved searches).