Change how folders open in the Finder on Mac
When you open a folder in the Finder, the folder’s contents usually replace the current contents of the window. If you prefer, you can open a folder in a new tab or window.
Set how all folders open
On your Mac, choose Apple menu
in the sidebar. (You may need to scroll down.)Go to Windows & Apps on the right, click the pop-up menu next to “Prefer tabs when opening documents”, then choose an option:
Never: Open folders in a new window, not a tab.
Always: Open folders in a new tab.
In Full Screen: Open folders in a tab only when you’re working in full screen.
Open a single folder
On your Mac, press the Command key while you double-click the folder.
The folder opens in a new tab or window, depending on your Finder settings. In the Finder, choose Finder > Settings, then click General. Select “Open folders in tabs instead of new windows” to have folders open in tabs; deselect it to have folders open in windows.
Tip: If the Finder toolbar and sidebar are hidden, double-clicking a folder without pressing the Command key opens the folder in a new window.
To open a new Finder window without opening a specific folder, click the Finder icon 
in the Dock, then choose File > New Finder Window or press Command-N.
Work with tabs
In the Finder on your Mac, do one of the following:
If all of your tabs aren’t visible, scroll through them.
When two or more tabs are open, click the Add button
to open a new tab.To close a tab, place the pointer over the tab, then click the Delete button
.