I had my floors redone about 5 years ago. The floors look in above average
condition. I'd like to apply another coat. There are a handful of areas I
need a little wood filler. Outside of adding some filler and sanding those
areas down, would there be anything else to do besides cleaning out dust and
adding another coat. Can an additional coat or two be applied to an entire
floor over the existing coats, or does the whole thing need to be sanded
down?

Overall, I'd like to add another coat or two to keep the floors in a
position so they don't need to be professionally done, yet I don't want to
mess them up.
Thanks for the suggestions!