Adding to Nat's thoughts, these methods may achieve your goal...
1. Load project #1
This is Sequence #1
2. Click the 'hamburger' menu (3-lines at top left of the window), click FILE, then click IMPORT CLIPS FROM ANOTHER PROJECT
The project that you select will be loaded into Sequence #2
Switch to Sequence #2 by clicking its tab above the timeline
Click in the thumbnails area and then press <ctrl-A> to select ALL. Now press <ctrl-C> to copy
Switch back to Sequence # 1 by clicking its tab.
Position the cursor (red line) at the end of the sequence (or at the spot where you want the other sequence to be added) and press <ctrl'V> to paste
This will add sequence two to sequence one, with all editable clips and tracks
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Another approach, if you simply want two completed projects back to back...
1. Load Sequence # with your first project
2. Create a second blank sequence by clicking the + sign at the right of a sequence tabs. Load project #2
3. Create a third blank sequence by clicking the + sign at the right of a sequence tabs
4. Above the bin (near the top-left of the window) click the SEQUENCES tab
5. Right-click on the Sequence #1 folder and PLACE ON SEQUENCE AT START
6. Right-click on the Sequence #2 folder and PLACE ON SEQUENCE AT END
Sequence #3 now contains two back-to-back projects as CLIPS (no individual edits)
All content is there, though the overlay and audio tracks will be blank
Export Sequence #3