I am often unsure, about wich tabs i should make, and where i should put my pets. I like the idea of having tags/groups a lot better. So you could predefine groups, and put your pets in multiple groups, and then filter for a specific set with checkboxes or something. Like:

"sale, gp1"    or   "unicorns, gp3, sale"   ...

I hope, you like the idea as much as i do.

Cya :)

I would support this exspecially if it also included automatic tags for a pet's status; pregnant, growing, taming, ect.

I like the idea of automatic groups :)

What about

1. default groups

• all ( default, when going to the pet's view )
• unicorn
• puma
• dragon
• cocatrice
• ...

2. automatic groups

• tamed
• pregnant
• young
• crafting
• training
• ...

3. user defined groups you pre-create yourself, and put your pets into like

• sale
• my most beloved ones
• killer unicorns
• breeders
• your group here ...

combine groups with tabs

by binding groups to tabs.
The "no group" tab would become "all",
and when creating new tabs, it gets a set of groups.

filter groups

• included [ checkbox for every group ]
• excluded [ checkbox for every group ]

example:

included: "my most beloved ones"
excluded: pregnant, puma
would give you all pets that are your most beloved ones, and not pregnant pumas ;)
if there is an exclude only, it means all but your exclude.

[edit]

multi-selects would be an option instead of checkboxes