2 data components in item definition

[sharp dagger]

so I have this item definition

{
  "model": {
    "type": "minecraft:select",
    "property": "minecraft:component",
    "component": "minecraft:custom_data",
    "cases": [
      {
        "when": {
          "dagger": true
        },
        "model": {
          "type": "minecraft:select",
          "property": "minecraft:component",
          "component": "minecraft:custom_data",
          "cases": [
            {
              "when": {
                "used": true
              },
              "model": {
                "type": "minecraft:model",
                "model": "cults:item/used_dagger"
              }
            }
          ],
          "fallback": {
            "type": "minecraft:model",
            "model": "cults:item/dagger"
          }
        }
      }
    ],
    "fallback": {
      "type": "minecraft:model",
      "model": "minecraft:item/iron_sword"
    }
  }
}

that's supposed to have a different model when the sword has custom data dagger and another one when it also has used
give @s iron_sword[minecraft:custom_data={"dagger":true}] has the correct model but
give @s iron_sword[minecraft:custom_data={"dagger":true,"used":true}] just has the default

[last pilot]

sometimes with custom data when detecting components instead of predicates in datapacks, it hasnt worked for items that have more custom data than you are detecting.

Might be same here for resourcepack itmes. For the used model, try doing

"when": {
    "used": true,
    "dagger": true
        },

not 100% sure this will work but lmk

[jagged bluff]

the component property type under select uses the direct component check, which means it will only show your model if the component exactly matches the item. you can use a predicate test with the condition model type for a predicate test on custom_data, but that starts to require awkward nesting
so i would generally instead recommend also adding custom_model_data and using the bespoke select property that exists for that component

(although for your case, condition might still be more than sufficient. just two layers necessary)