I was planning to travel to New York this coming April but with the virus I cancelled the flight.  I still have a Re-Entry Permit in my passport.  I also plan to leave in mid July to HCMC to change the type of visa I have to an Non 0 for marriage.  I will be leaving 10 prior to my current extension ends.  What can be done about the Re-Entry Permit?

You do not have to leave the country to change the reason for your extension of stay to marriage. 

Do you have a single or multiple re-entry permit? If a single you could do a border hop to use it.

Normally though immigration will not insist on using the re-entry permit if you have a visa that allows a longer stay than it does.

You need to do nothing. Immigration just ignore it ,,,,used or not