That would probably be very hard to do since chapter 3, page 15 of the service manual indicates one of the parts you need isn't for sale.
(5) Hard drive connector cable L72698-001 (6) Hard drive bracket not available as spare part
It would be a lot easier to replace your existing M.2 SSD with one with a larger storage capacity.
Plus you would be saving on battery power not running an extra device.
As far as the warranty...this is a peer to peer forum and we are not authorized to reply on behalf of HP regarding the warranty terms.
If you look at chapter 5, removing and replacing the hard drive, SSD and memory are customer authorized procedures.
However this note at the top of chapter 5 applies...
NOTE: The Customer Self-Repair program is not available in all locations. Installing a part not supported by the Customer Self-Repair program may void your warranty. Check your warranty to determine if Customer Self-Repair is supported in your location.
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