There was a point that was able able to use NPC's in Creative. The pack shown in the video linked below is one that I have been working on for my family's Realm. You can see in the Survival half that this GUI is packed with options. But in Creative, I can't get past the first part of the dialogue (which the initial button is part of the NPC herself and properly calls the JSON dialogue). I was able to beta test my work in the last version of MC from calling each individual scene (given some scenes required a certain player to open). However in 1.18.10, sub-dialogues won't open.

Video: NPC dialogues fail to open in Creative

Steps to Reproduce:

1. Create a NPC behaviour pack with at least 2 or 3 scenes. Ensure the additional scenes are called from the first.
2. Launch a world and /summon npc
3. Use button mode (NPC setup prevents use of on-open commands) to call the first scene of the pack you just made then exit to save the edits.
4. While in creative, open the NPC followed by Edit Dialogue and tap/click the button. This should have opened your first scene
5. Press on the button for the second scene. This would have failed to open.
6. Switch to survival and repeat steps 4 and 5. This time, however, the second scene should open.

Expected Result:
The second scene opens upon pressing the button regardless of game more.

Observed Result:

The second scene fails upon pressing the button while in Creative.