Joining Camera Video Files

I have a Panasonic Lumix FZ1000, bought recently, but a 2015 design. I love the 16x optical zoom Leica lens, all the SLR-like controls, and it captures 4K (3840 x 2160 pixels) video! But — like many cameras — it insists on splitting a video recording into 4Gb chunks. This made sense in an era…