Few Suggestions
My first and main suggestion is to make the SUM feature add up all numbers shown, even if there are words or symbols after them. Or make it so that if you have a number with a period after it still SUMs with the rest of the numbers. I have custom dice with effects as well that I still want to sum with my other non-effect dice.
My other suggestion is to add the ability to add emoji to the custom dice! This would allow you to create dice with more graphic symbols.
Hope you consider my suggestions and keep up the great work :)