Pressure groups are mainly used for tables. Computers do not show you pressure groups - at least two of mine do not. I am not sure that Pressure Groups are important for logging but that is my opinion. Most instructors want to see how many dives and what type of diving you have done. This gives them a better idea of your diving experience and then when they get you in the water they can evaluate your skill level.
There is a way to use the tables to do multilevel diving but it is not condoned by any agencies so it is not worth discussing. I have used it and still use it to plan my dives including gas volume and reserves.
Good luck in your diving.