Hello, everyone! First time posting, probably posting in the wrong place. If so, apologies in advance.

I am extremely new to actually playing D&D. I have some theoretical knowledge from watching/listening to Critical Role and other shows, but mostly, I've been using the framework of D&D as a writing prompt (I love writing!) and/or attempting to play solo, because no one in my immediate social circle is into it and playing with strangers online just doesn't appeal to me for a number of reasons.

I've built a fair few characters for fun and the D&D Beyond character builder has truly been a blessing, but now I'm a little stuck, and it is the worst possible time to be stuck, because I might actually be playing this character with a friend in the future and I want her character sheet to be all spit-and-polished.

I have a two-fold question about the Improved Minor Illusion feature. The description says the following:

When you choose this school at 2nd level, you learn the minor illusion cantrip. If you already know this cantrip, you learn a different wizard cantrip of your choice.

Does this rule apply even if the character innately knows the cantrip on account of their race, rather than because they studied it as a wizard? She's an adorable little forest gnome, and I find that this feature creates a strange little overlap with the Natural Illusionist racial trait that I haven't yet been able to solve because my ability to make the best of D&D Beyond is less than perfect.

I noticed that on my current, in-progress character sheet, minor illusion appears twice, once with Natural Illusionist as its source and once because of Improved Minor Illusion.

So my questions are:

a) Am I allowed to switch the second one with something else, or does the rule only apply if the cantrip is learned, not innate?

b) If I'm allowed, how do I even do it on the D&D Beyond character builder? As it stands, I can consult my list of spells, click the offending item, and then open up the "Customize" part, but I don't know where to go from there. Is that the correct way to substitute a spell for another in this situation? I can't just have my character "unlearn" it and switch it out, because it was never learned in the first place, so when I go back to the editing mode, it doesn't show up in the spellbook for me to remove. So can I use the "Customize" feature to make the switch? If so, how? I've never done such an advanced level of customization before and I don't know how to do it properly.

Thanks in advance!

Yeah it's a known issue they haven't got around to fixing.

So, yes, to clarify, upon reaching 2nd level you get Minor Illusion, if you already know this from any other source, you can choose a different cantrip. 

To resolve you need to use the Homebrew tools. Your options are:

1. Make a copy of the Forest Gnome race and change Minor Illusion to a different cantrip you want.

OR

2. Make a copy of the School of Illusion Wizard subclass and edit it to provide a different cantrip.

OR

Create a new homebrew feat to grant the cantrip. Add the feat to the character.

Thank you! Literally none of this would have occurred to me, I'll get on it ASAP.