Update: v1.44 you can now simply drag many of the views, including "Search" from the sidebar to the panel and back. See https://code.visualstudio.com/updates/v1_44#_increased-view-placement-flexibility and https://stackoverflow.com/a/55981465/836330
Update: v1.42 added a context menu option
Move to Panel/Move to Sidebar
to certain typically sidebar views like Search, Outline and custom views. So you wouldn't have to use a setting to move the Search view back to the sidebar. Here is a demo:
Also notice that you no longer right-click in the empty space below the search inputs in the sidebar but on/near the Search header itself to bring up the toggle option.
As part of the v1.42 release the search.location setting mentioned below will be deprecated.
Your setting should migrate automatically, but you will need to use
the new generalized method to move the Search view going forward. You
do not need to enable the experimental preview setting above in order
to move the Search view with the new context menu entry.
So I don't think there is a setting anymore, you just right-click on the header text "Search" whether it is in the Panel or active in the Sidebar to move it. See the demo below.
Right-click on the "Search" header if you have it in the sidebar to "Move to Panel".
If Search is in the panel, right-click on the word Search to "Move to Sidebar".
To enable moving the Output view at this point, you need to enable workbench.view.experimental.allowMovingToNewContainer.
There is a new unbound command workbench.view.search.moveView which you can use to toggle the search position between the panel and sidebar. But note that in my testing it only works a couple of times because it focuses the panel when you move search to the sidebar - I'll file a bug.
Previous Answer::
You may have modified the setting:
"search.location": "sidebar",
which is the default to the alternative
"search.location": "panel",
which would put the search widget into the terminal panel as another tab.
As of vscode v1.35 or so, you can now right-click in the empty space below the search view (i.e., in the sidebar under the open search inputs) and you will get an option to Toggle Search View Position.
This context menu switch of the search view is persistent. It will automatically add this setting to your settings.json:
"search.location": "panel",
The only way at present (but see edit just below) to move the icon back to the activity bar (and thus the search across files functionality to the sidebar) is to change that setting to the sidebar option. Or look for this setting in the settings editor:
Search: Location
Controls whether the search will be shown as a view
in the sidebar or as a panel in the panel area for more horizontal
space.
EDIT: More recently, vscode added the abilty to right-click in the search area when it is in the panel to toggle it back to the sidebar.
