It doesn't work anymore in Bryce 7.1. In some earlier versions opened labs were displayed on the second monitor. The option, as it was implemented (and when it worked) was not of much use.
EDIT to add: It was introduced with Bryce 7.0 and it works, opened labs appear on the second screen. Bryce 7.1 doesn't show an opened lab if the option is enabled. When the option is disabled, the opened lab appears. Always only on one screen. Obviously, that option broke between 7.0 and 7.1.
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It doesn't work anymore in Bryce 7.1. In some earlier versions opened labs were displayed on the second monitor. The option, as it was implemented (and when it worked) was not of much use.
EDIT to add: It was introduced with Bryce 7.0 and it works, opened labs appear on the second screen. Bryce 7.1 doesn't show an opened lab if the option is enabled. When the option is disabled, the opened lab appears. Always only on one screen. Obviously, that option broke between 7.0 and 7.1.