I want to start this off by saying that I am not claiming that I am the first person to have thought of these! I have not checked if these ideas are original, but all credit goes to the people who thought of these first!
feel free to comment any ideas you have :)

Anywho… here’s the list:

CURLED EARS
similar to the already existing ‘foldies’, could be cute curled-eared lions!

CURLED TAIL
a tail that curls back on itself in the same way that dog breed’s tails like the samoyed or shiba inu.

LOP EARS
another possible mutation to give you your daily dose of serotonin! imagine little cubs with floppy ears! adorable!

MUNCHKIN
a gene that causes short legs in domestic cats. it is not considered a disability and despite concerns of spinal problems and impaired mobility, these felines are perfectly healthy!
keep in mind, this may be classified under the pre-existing mutation in this game, “dwarfism”.

NO FUR
bald lions! oh my goodness! are they cute.. or creepy..? that’s for you to decide!

POLYDACTYL
a condition characterised by extra toes. most of the time it doesn’t have much of an effect on the animal, and would be a super cute addition to the game! five toes is already adorable, imagine what more would be like!

SPARSE HAIR
need some nightmare-fuel perhaps? what about a unique-looking sparse-furred lion. the gene would likely only affect females, much like mane mutations and overgrown fur. these lions could have a werewolf-like charm, similar to the lykoi breed found in domestic felines.

SYNDACTYLY
this gene is present among many animals, including domestic felines and even humans. it is characterised by the fusing of toes; the opposite of polydactyl. most cats with this condition are not severely affected as long as their claws are clipped. however, for this game, I’d suggest this be made a lethal mutation, or a mutation with about a 25% fatality rate, since lions are wild animals and this condition could hinder their ability to hunt.