Hi @bbkleather
I did some looking into this and was able to replicate this myself on both my android and apple device. I have brought this to the attention of our technical team and they are currently reviewing to see if this was a feature left out at this time or if it is a technical issue with the admin app.
I sincerely thank you for flagging this! As a work around on your mobile device, you can sign into your store admin from within the browser instead of the admin app to create your draft orders. This should allow you to create custom items while also applying a shipping weight to it as well.
I’ll update you here once I know more!