It is possible with the paragraph property Balance Ragged Lines, but the required value for this is – strangely – not available in the regular User interface. The interface only allows a yes/no, but the Scripting Interface reveals there are actually more choices available to the formatting engine:
BalanceLinesStyle.FULLY_BALANCED Balances lines equally.
BalanceLinesStyle.NO_BALANCING Does not balance lines.
BalanceLinesStyle.PYRAMID_SHAPE Prefers longer last lines.
BalanceLinesStyle.VEE_SHAPE Prefers shorter last lines.
(http://jongware.mit.edu/idcs5/pe_BalanceLinesStyle.html)
The UI Off setting corresponds to BalanceLinesStyle.NO_BALANCING
and the On to BalanceLinesStyle.VEE_SHAPE
, so the default indeed seems to prefer a longer first line.
If you run this one-line Javascript with the text cursor inside the paragraph to change, you can see it toggles around to prefer shorter first lines instead:
app.selection[0].balanceRaggedLines = BalanceLinesStyle.PYRAMID_SHAPE;
And if you check the paragraph overrides, you can see it is actually recorded as "... + balance: pyramid shape".
Do note that the rule "make the lines as evenly long as possible" still prevails, and so this will still favor
Lorem ipsum
dolor sit amet
over
Lorem ipsum dolor
sit amet
It may work for other texts, though.