I tried to create recipe using potion fluid that create added:
event.recipes.createMixing(Fluid.of('create:potion', 1000, {Potion: "minecraft:regeneration"}), [
'create:honeyed_apple',
Fluid.of('create:potion', 1000, {Potion: "minecraft:awkward"})
]).heated()
but i get this error:
[WARN ] Error creating recipe create:kjs_bsgx6r45fehfywrczzk0j50y1[create:mixing]: {"processingTime":100,"heatRequirement":"heated","type":"create:mixing","ingredients":[{"item":"create:honeyed_apple"},{"fluid":"create:potion","nbt":{"Potion":"minecraft:awkward"},"amount":1000}],"results":[{"fluid":"create:potion","amount":1000,"nbt":null}]}: com.google.gson.JsonSyntaxException: Expected nbt to be a string, was null (json)

However, using potion nbt in ingredients is working
event.recipes.createMixing('createdeco:netherite_nugget', [
Fluid.of('create:potion', 50, {Potion: "minecraft:regeneration"}),
'create:cinder_flour',
'minecraft:magma_cream'
])
This works

event.custom({
"processingTime": 100,
"heatRequirement":"heated",
"type":"create:mixing",
"ingredients":[
{"item":"create:honeyed_apple"},
{"fluid":"create:potion", "nbt":{"Potion":"minecraft:awkward"}, "amount":1000}
],
"results":[{"fluid":"create:potion","amount":1000,"nbt":{"Potion":"minecraft:regeneration"}}]
})
This does not work either.