>>Option to lock first line when using CSV / TSV / DSV mode

It’s already possible:

– execute Window > Split
– split to two horizontal panes (put the vertical delimiter far to the right to not split vertically),
—- while making the top of both panels very small, so you just see the first lines.

Now you can scroll the file in the lower pane as far as you like, while seeing the header line still in the upper pane.