From the sound of your description, it seems like you use the AMS.
It’s true, the type of filament loaded in the AMS is not fully customizable. On the other hand, the settings are coming from the sliced file and it doesn’t ‘care’ what type of filament is loaded in the AMS. The only restriction is that the type (e.g. PLA) has to match between the sliced file and the AMS.
That means, modify the existing generic PLA filament in the slicer to your needs, save it as a new profile (keep PLA as type). Use the new profile when slicing your object to print. When sending to the printer it will ask you which slots you want to use (if the colors are matching, it prepopolate the slots matching), confirm and print.
Don’t reload from the AMS - otherwise it will also preload again the generic profile.