WildBillG, I guess the short answer is that yes, you can get a list of powders that will perform within various parameters in a given cartridge. I've used it often. You can choose for example a 35 Whelen, shooting a 225 grain Nosler, and set up the parameters of say less than 100% fill (uncompressed) and greater than 85%; plus 60,000 PSI max chamber pressure; and it will generate a list of powders, plus the charge weights, that will get to that PSI, and give the muzzle velocities, % burn, etc. As wildcat455 said, though, it is best used to set up the bottom rounds for your ladder or OCW exercise. Once you have some actual performance data from your brass, rifle, and powder you can fine tune things like burn rate in the program and create a new file that you name something like "My Rem700 Whelen", and you can come back to it often. I have gotten QL to perform well within the SD for several cartridges after doing so. Another thing you can do is tune to an "optimal barrel time" (OBT) node because time to muzzle is one solution generated. I have for example an OBT spreadsheet in Excel for a 200 gr. Swift A-frame I was testing in my 300 WSM Tikka. It won't upload here, I guess this site wont accept .xlsx files, but it shows 47 powders that will hit that OBT node and remain below max pressures, under 100% charge, and over 83% charge, with the velocities, chamber pressures, burn % and muzzle pressure for each one.
The sheer number of variables you can fiddle with is a good and a bad thing; I spent several months just practicing with the program before I used it for real.
Look up some of Chris Long's papers for a discussion of how to fiddle with QL and the OBT method, he is really good.