now the contents of "Project Explorer" should be this one below
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title
Application Project "demo", BSP and reference hardware checked
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now you should copy the contents of the original demo (all .c and .h files from "TE0xxx-Reference-Designs\reference-TE0xxx\SDK\SDK_Workspace\demo\src" already moved in the temporary folder "C:\demo_src_TE") inside the folder "C:\XilinxProject\reference-TE0xxx\SDK\SDK_Workspace\demo\scr" as already do in the figure above;
now you should select "src" folder in "Project Explorer" > "demo", right click and select "Refresh";