Usually I use PDP giving access to some areas, but for exceptions I can not just give access to everything, like Employees of Area A but not access to a specific employee out of 300 is posible to use a not in for a PDP?
Easiest way I can think of would be to create new calculated fields in a dataflow that flag for the conditions you want to set. This way you can use multiple conditions including "not in" to create a value in the column and then use that field in a PDP policy.
Due to standard security practices a NOT IN option typically isn't provided as it opens up the data possibly to everyone on accident rather than just a single person on accident. NOT IN is a more risky security practice which is why Domo doesn't include it.
Alternatively, you could configure specific groups to not include that specific user and then set access to that group.