You can use a workaround by creating a calendar that defines 1 minute a day,
say 12:00am to 00:01 as the working time and putting a fictitious task that
uses it as the task calendar in the middle of the link between the task in
question and its predecessor, but this is only a partial solution. Work
only takes place on the working time calendar and MSP will never schedule
OT, ie, work outside the working time calendar, on its own. So what happens
if your regular work schedule is 8-12 and 1-5 and the task you need to have
done in 1 continuous unbroken time period happens to be a 12 hour task?
There is no place that a task requiring 12 hours continuous work can be put
on a work schedule that has a maximum unbroken sequence of 4 hours of work
before the resource goes away for a time so we still have to revert back to
manually scheduling it in some way either by adding OT work or defining a 12
hour task calendar for it.