I would be surprised if you were legally allowed to go and modify assets before the will is executed.

I know when my partner died that I was not supposed to log in to her accounts and just transfer shit around; banks instead have very well defined processes for working out who is the legally correct person to do that and then empowering them to do so.

Remember, banks and other big companies deal with this all the time. They necessarily must have robust processes for doing it with the existing societal/legal systems of establishing who is the ‘right person’.