I have a model which requires TPU for the entire print and the four PLA colors on only the first layer mixed in with the TPU. How can I make the printer print all PLA filament first and then disconnect the ams hub and put the TPU in to finish out the print?
Never tried that. Not sure if it lets you flip back and forth between the external spool holder and AMS in the same print. You could use the Ext Spool holder the whole way and add a pause in the slicer for the material changes. But I don’t know if you can flip between AMS and the Ext. Spool. Hopefully someone can answer that.
Yeah, it’s more so that I want to tell the printer to do all four ams spools first then when they are finished(only first layer), then the tpu will be switched and print the rest. Basically I want to say do TPU last, but I’m not sure how to do that.
I have not try this on the Bambu lab x1 AMS 
I have used custom g-code and Z offsets to do this on my other printer when doing custom stuff and using the palette pro mixing filaments so this might be the way to do it on the Bambu lab.
I know Simplity3D has a variable height wizard. I have used the version 4 and they support up to 6 extruders and version 5 is said to work with the Bambu Labs and AMS might be an option for you but its not free software you can look into this more also.
I suppose you could add a manual pause after the first layer and switch to the external spool there.
Although it’s a bit sad, that Bambu Studio doesn’t seem to allow the external spool to be selected as material for slicing. So you may also need to manually adjust temperature settings on the printer when swapping the filament during the pause.
Why couldn’t it just prompt you to manually load filament when the external spool was being selected. This would allow you to use TPU with PLA. or other material prints. I like this idea, it would use the filament run-out sensor to detect no filament and prompt you to load external filament. This would require the Y connector to make it happen effectively. Having an additional AMS would not solve the need for a TPU combined with other materials print.