I figured out how to group (assemble) objects together before importing to Bambu Studio/OrcaSlicer. In Blender you can create an Empty object and either
- Drag your objects into the Empty to group them together.
- Select the objects to group together and select the Empty last. Then Ctrl+P > Parent under Object.
Now you only need to import a single 3MF file with all your pregrouped objects together and they are in multiple assemblies. Not the solution to the original question of disabling drop to bed but it’s an acceptable work around that saves time.