As the description says, the Rocket Trio first encountered this Chewtle as a wild Pokemon in JN013 "The Climb to Be the Very Best!". Long story short, it and the episode before it had a rampaging Gigantamax Drednaw in Wyndon Stadium that Ash & Goh had to battle (Pikachu also suddenly Gigantamaxing). With helpful advice from Leon, they're able to defeat the Drednaw and send it flying (that's the last we saw of the Drednaw). The Rocket Trio, Seeing how strong the Drednaw was, decided to go capture it. After a scene where Ash learns about the World Coronation Series and decides to join it (as well as Leon meeting up with Ash to accept an earlier battle request; obviously Ash loses the battle but Leon was still impressed so let's him keep the Dynamax Band he lent to him for the battle and says he'll be expecting Ash to make a top spot in the World Coronation Series), we come back to the Rocket Trio to see they've been searching all night for the Drednaw but no results. Suddenly they noticed this Chewtle hanging off Jessie's hair and, learning it evolves into Drednaw, catch it and declare their mission a success.
Note a gimmick with the Rocket Trio this gen is that, instead of having a set party of Pokemon (only "set" Pokemon is Meowth, Wobbuffet, Pelipper, and sort this Chewtle), when a battle starts a Pelipper owned by Team Rocket (hey, what happened to Delibird?) delivers them the "Rocket Prize Master". It's essentially a vending machine filled with Team Rocket branded Poke Balls, a new secret weapon overseen by Giovanni to provide agents with powerful Pokemon while on the field (though they don't know what Pokemon they're getting when they use it, but each ball has a piece of paper that tells them about the Pokemon inside; not so sure about the random factor there Giovanni), and he gives the Rocket Trio early access to it in JN003 "Ivysaur's Mysterious Tower!". It's pretty much another way for the writers to include more Pokemon in this season as well as provide some more interesting battles with the Rocket Trio.
Anyway, during a battle with Ash & Goh in JN017 "Kicking It from Here Into Tomorrow!", Jessie's Rocket Prize Master Pokemon is Chewtle which the Rocket Trio recognize as the Chewtle they had caught a few episodes ago. Though they sent it to Rocket HQ & Giovanni, it looked to have been decided to add it to the Rocket Prize Master. It battled well but was eventually defeated and blasted off with the Rocket Trio.
Skipping the cameo episode, it's next major (and most recent) appearance was JN058. This episode is split into two (another new thing in this gen), Chewtle isn't in the first part "A Rollicking Roll..." but it's in the second part titled "Eyes on the Goal". In the second part it frees itself from its Poke Ball after Meowth and Wobbuffet accidentally vend its Poke Ball from the Rocket Prize Master and it goes for a walk where it encounters a Turtwig and they form a rivalry and race one another. It's a simply funny episode to just feature all the turtle Pokemon, at the end the other turtle Pokemon return to their trainer the Turtle Sage leaving Chewtle the only one left in the race thus winning, bragging its victory to Meowth & Wobbuffet. Presumably they went back to the base and Chewtle returned into its Poke Ball and put back into the Rocket Prize Master.
So, yeah, nothing really that special about it. It's just one of the recurring Pokemon which each gen has a few of, except its not wild but rather with the Rocket Trio for occasionally appearances likely for a gag. I imagine in the future they'll evolve it to a Drednaw and either discover it can Gigantamax or it can't, and if it can't likely learn there's a way to make it Gigantamax so could be a way to incorporate the Isle of Armor.
