you will need to start getting acquainted with the terms and what they mean
this is the navigation for the top area of your site.
your subsites can inherit the navigation from the parent site and it will look the same, while being managed at the top site
the current navigation, aka quick launch navigation, displays items that belong to the current site you are located in, placing them at the left area. you can inherit the setting, but typically each site will show its own items based on what lists exist in that site
quick launch is the control that displays items in the left area of each site. it is specific of each site.
the tree view is another control, usually rendered below quick launch, that displays the current site's content in a sort of "tree" control with their icons, and expand/collapse function
this is also specific of each site
you can enable and disable both quick launch and tree view on any site through "Navigation Elements" or by going to
if you want to make a reusable left navigation, you can take advantage of Metadata Navigation using terms in a term set configured to be used for navigation
same tree view on subsites
from what I understand, you want to make the treeview control display the same data on all sites and subsites (if you just want to enable it, see above and stop reading!)
although this is not the intended default behavior, it is possible through some tweaks as mentioned here
an example implementation would be:
- create a new file under _catalogs\masterpage called seattle_custom.master (you can go to Files > Blank Master Page in SharePoint Designer).
- copy the contents of seattle.master to it
- locate SPHierarchyDataSourceControl and ensure you have this
where the guid is the id of your root web.
to find the id of the root web, open the root web, open the browser console and type
- save, check in and publish the master page file
- pick the new master page under master page options to enable it and reset it for all sites
the tree view is now showing content from the point of view of the root web
please note that generally speaking we are advised against making master page changes, as they might cause issues when new updates are rolled out, but at least you're creating your own and not touching the ootb one