Creating CSV with geometry as WKT in QGIS (with choosing field delimiter)

I was able to export to CSV, using other than a comma, by separating the layer creation options in the Save As.. dialog with linebreaks.

Neither comma, nor space-separating them (even when they were in quotes) worked, but the linebreaks did the trick. To emphasize..

THIS APPROACH WORKED (linebreak-separated):

GEOMETRY=AS_WKT
SEPARATOR=SEMICOLON
LINEFORMAT=CRLF

But these approaches did NOT work...

(space-separated options):

GEOMETRY=AS_WKT SEPARATOR=SEMICOLON

(comma-separated options):

GEOMETRY=AS_WKT, SEPARATOR=SEMICOLON

(quoted, and either space or comma-separated LCOs):

"GEOMETRY=AS_WKT", "SEPARATOR=SEMICOLON"

As @underdark noted, there are some additional options discussed on the OGR CSV driver page you may want to be aware of. Specifically, the SEPARATOR parameter will accept either SEMICOLON or TAB in addition to COMMA. Also, you may want to experiment with the LINEFORMAT parameter, which supports either CRLF (dos/windows) or LF (unix).

A picture says a thousand words, so here's a screen grab. :)

Settings for QGIS 3 using "Layer Options":