Display horizontal scrollbar in text editor

[JetStarBlues]

How can I get a horizontal scrollbar to appear for the text editor*?
It is a bit limiting to have to find the longest line, in order to be able to scroll across the full length...

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*I am not sure if text editor is the correct name... Looking at the 'overview.c' code, the "text editor" seems to be generated by nk_edit_string in the following lines:

nk_layout_row_static( ctx, 180, 278, 1 );

nk_edit_string(

	ctx,
	NK_EDIT_BOX,
	box_buffer,
	&box_len,
	512,
	nk_filter_default
);