I havent tested this out, but i was looking through the campaign maps and found what looks to be a solution to this.
Unit - Order Ultralisk (Burrowed) [13.93, 25.62] to (Turn Zergling - Unburrow auto cast Off) (Replace Existing Orders)
you need to turn off auto casting of unburrow, i found this in zeratul's first map. ill look into it more to see if anything else is needed for this to work right
EDIT: Ok i tested it out and its actually very simple to get a unit to stay burrowed until somthing comes into view or is detected. Make sure you research burrow for the computer player you are using these commands on
basically at map initialazation you issue orders as follows to keep a specific ultralisk burrowed, it can also be modified for unit groups
Unit - Order Ultralisk [70.96, 201.69] to (Ultralisk - Burrow) (Replace Existing Orders)
General - Wait 1.0 Game Time seconds
Unit - Order Ultralisk [70.96, 201.69] to (Turn Ultralisk - Unburrow auto cast On) (Replace Existing Orders)
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I havent tested this out, but i was looking through the campaign maps and found what looks to be a solution to this.
Unit - Order Ultralisk (Burrowed) [13.93, 25.62] to (Turn Zergling - Unburrow auto cast Off) (Replace Existing Orders)
you need to turn off auto casting of unburrow, i found this in zeratul's first map. ill look into it more to see if anything else is needed for this to work right
EDIT: Ok i tested it out and its actually very simple to get a unit to stay burrowed until somthing comes into view or is detected. Make sure you research burrow for the computer player you are using these commands on
basically at map initialazation you issue orders as follows to keep a specific ultralisk burrowed, it can also be modified for unit groups
Unit - Order Ultralisk [70.96, 201.69] to (Ultralisk - Burrow) (Replace Existing Orders)
General - Wait 1.0 Game Time seconds
Unit - Order Ultralisk [70.96, 201.69] to (Turn Ultralisk - Unburrow auto cast On) (Replace Existing Orders)