Just in case you're trying to get this list of bare keys so you can copy/paste it somewhere else (like Excel), I'll throw out another option that may be helpful and save some scrolling:
:sort INVENTORY TO DELIM 9 /tmp/inventory.txt
Will run your command and dump the output (tab-delimited, though that's irrelevant with only one field) to a file in the tmp directory.
:UDT.OPTIONS 91 ON
Is helpful if you're dumping dates, numbers or anything that needs output formatting.
UDT Options Command reference describes that:
UDT.OPTIONS 91 U_LIST_TO_CONV
affects saved queries on
data that is defined in the dictionary with a conversion code. For
example, when a date is defined as D4, the internal date is 9611,
which the conversion code translates as 04/24/94. UniData does not
convert the data before it saves UniQuery results to an ASCII file.
With UDT.OPTIONS 91, you can force the conversion before UniData saves
the ASCII file.