Creatures section for renaming and adding notes works exactly like it does for equipment in the character sheet. Say you have petDire Wolfor whatever animal or monster, once added as a pet, familiar, mount, etc. you then mouse click on its standard name and a side window springs out and there in that side menu you look for a bold Customizeand click on that and below that a drop down with a blank field appears with Nameon the left of the field. So that field you fill in and whatever you type in will override what its usual name is. I usually keep the of the original name in parathesis so mine usually looks like its name and creature type so this example would be... Spot (Dire Wolf) and both show up as the end result but you can do the custom name however you please. Further down past, that field is size, type,alignment, etc.that you can also easily customize or not as you please. Below those is a blank called notesfiled add whatever as well as misc. catch-all field.
All same, same as equipment where if you want to rename your short sword and call is Pig-Sticker! Hope that is of some help... but from what it sounds like what you want to do is totally doable!