Go to the My Product Listings page from your dashboard. See mine: Custom Categories
Select Manage Your Categories at the bottom of the list. The edit view is this:
Go to your emoji keyboard, on your iPad, and try some out. Once you commit, you will see if it worked or not by seeing the saved visual after you click.
If it did not, the category will be empty of all text, but still indicate how many projects are in the category. I suggest only changing one category at a time!
This will require some trial and error time, as some emojis do not work.
I hope this helps! Thanks for checking in, and check out a category which may be useful to you while you are at it!
All the best in customizing your page!