Have you tried using the DVD order available on TheTVDB?
https://www.thetvdb.com/series/star-wars-rebels/seasons/dvd/1
https://www.thetvdb.com/series/star-wars-rebels/seasons/dvd/2
That ordering shows the episodes you mention at the start of their respective seasons. For the best results you may want to combine the two-part episodes into single files using the instructions here, as they’re considered single, longer episodes:
To use DVD order in Plex Media Server, open edit the properties for the series at the show-level and set the Episode ordering to DVD order on the advanced tab:
