These are the 3 episodes from the rebels era. The one with Ahsoka training Ezra has probably the most potential to fit in somewhere and add to the story. But who knows, maybe there is a place where the other 2 can come in handy.
https://youtu.be/0rlugDqJOJ8?feature=shared
Have been thinking about these and wanted to just throw an idea your way: The Ahsoka training Ezra scene could be a cold opening for s02ep01. This would give you the opportunity to cut off the kiddy dialogue in the end and go to black/introduction sequence instead. And the intro would be a nice seperator for different art styles.
Also there are 2 more I overlooked:
https://youtu.be/GUs_XuFWh3Q?si=V7ekO4s__x38u6Lk
https://youtu.be/rdofQfnDd8U?si=9K88U36tArZrv6bt
Since there are 5 in total, maybe using a few of them as cold opens could be cool?