[How can I input and output hex color values in Designer and Photos for iPad?]

It's hard to see how an app that's supposed to be relied on in a professional production environment could fail to accept hex code input. I'd recommend that your engineers make that a priority.

[Resize - By Percent]

I had to Google for an answer to the question of how to scale items by percentages. Found it here: 

 

Briefly, in the Transform panel, you can enter an equation in either the W or H field, using this expression:

 

PERCENTAGE: *=X% (e.g., scale to 50%)

MULTIPLY: *=X.x (e.g., multiply by 1.2)

DIVISION: /=X (e.g., divide by 3)

 

The video's narrator also says you can use plus or minus, but doesn't demonstrate.