IPad pro 11 magic keyboard slow charging

I suggest contacting/reaching out to Apple Product support and services.

Tap on the first link below and scroll down some to get to the Apple Product Support section and phone numbers for your location/region.

https://www.apple.com/contact/

OR

https://support.apple.com/en-us/HT201232

If you need to, if initial 1st tier Apple customer support is of no help to you, you can calmly ask to have this issue escalated up to more responsible, senior level Apple customer support employees to see if they can come up with other possible advice/solutions to this iPad Pro/Magic Keyboard charging issues, but I make no guarantees, whatsoever.

If need be, you can have your iPad issues escalated all the way up the chain to Apple engineering level customer phone support.

Even if no acceptable resolution, Apple, AT LEAST, logs all support calls and issues.

Best of Luck to You!

Even though the iPad will charge a bit slower using the pass through port in the keyboard, 2% in 8 hours is not acceptable, UNLESS the iPad was running, as in perhaps streaming music or videos? If the iPad was locked and nothing was nothing, I would recommend scheduling an appointment at your Apple Store Genius Bar and show it to them.

Are you using the iPad while it is actually trying to charge?

Are you plugged in to charge through the pass through charging port on the keyboard? If you are, it won't charge as quickly if you charge plugged directly into the iPad.