Currently, the CSV Import function of Yahoo Finance is accepting this kind of CSV file:

Symbol,Trade Date,Purchase Price,Quantity
GOOG,2018-07-05,281.79,10

which track BUY transactions only.
But I also need to import SELL transactions, which my broker gives me in their export.

I've tried all these combinations without any success:
Symbol,Trade Date,Purchase Price,Quantity
GOOG,2018-07-05,281.79,-10
GOOG,2018-07-05,-281.79,10
GOOG,2018-07-05,-281.79,-10

Can you please modify the CSV import feature so that it can accept also SELL transactions?
It could be something like a new "Type" column:
Symbol,Trade Date,Purchase Price,Quantity,Type
GOOG,2018-07-05,281.79,10,BUY
GOOG,2026-08-09,1234.56,10,SELL

Thankyou.