Can anyone really be upset with a good body swap episode? Either way, 'Once Upon a Swap' is a decent example of what Owl House "filler episodes" should be.
It provides a small bit of insight into the relationship between Eda and Lilith while also exploring the latter's motives. This small bit is still enough to be both interesting and engaging - encouraging further viewing for the rest of the season to get the eventual pay-off of Eda's and Lilith's confrontations.
The other two plot lines following King in Luz' body and Eda's in King's body are entertaining on their own too, without the need for lore and story like mentioned above.
It provides a small bit of insight into the relationship between Eda and Lilith while also exploring the latter's motives. This small bit is still enough to be both interesting and engaging - encouraging further viewing for the rest of the season to get the eventual pay-off of Eda's and Lilith's confrontations.
The other two plot lines following King in Luz' body and Eda's in King's body are entertaining on their own too, without the need for lore and story like mentioned above.