Normally reactions (you can add on long press the reaction symbol)
But in 94.1 version you can start typing : and you can add the gif from these collections by pressing the button on the right
Discussion
Like this:
brings up the custom emojis i've created. i guess it would only be gifs i've created
Had had to switched nostr:nprofile1qqs24yz8xftq8kkdf7q5yzf4v7tn2ek78v0zp2y427mj3sa7f34ggjcpzamhxue69uhhv6t5daezumn0wd68yvfwvdhk6tcppemhxue69uhkummn9ekx7mp0qyg8wumn8ghj7mn0wd68ytnddakj703s8dt version to nostr:nprofile1qqs83nn04fezvsu89p8xg7axjwye2u67errat3dx2um725fs7qnrqlgzqtdq0 to get this feature, as the update was still not available on Google Play. Thanks! 🙌 
Zapstore and Obtainium are the better way anyways 🤙