About ynab: Is there a way to track a child's savings account/investment? EG lets say a child (adult child or whatever) has money in a savings/investment account (or trust fund) and that will be available for his wedding in the future. You want to keep note of that, add that to the savings amount and link it to his wedding (as opposed to a different child's wedding). How / Can you do that on ynab?

I would not recommend doing this in YNAB, and would rather use a Monte Carlo software for this like right capital or projection labs, but you could absolutely track it in YNAB and then all the money for that account can be assigned to the target associated with that child's wedding.