What if

If I had 5 gallon pots but only 3gal. Dirt. The whole veg. Then Added the remaining 2 gallon dirt at beginning of flower would the stalk that gets coverd turn into root and help them. Any words of wisdom are appreciated.

Not a good idea to cover the main stem once flowering has started. It will spend time from flowering to grow more roots reducing yield.

Lol -
Take the 3 gallon plant Out of 5 gallon container, put 2 gallons of new soil in empty 5 gallon container, repot 3 gallon plant into the new 2 gallons of soil, fill in round edges and viola, problem solved!
Lol

yeah, top dressing isn't the best plan, roots grow downwards naturally. the stem will grow roots if you bury it, but it will take a lot more of the plants resources than repotting in more soil and letting the roots do what they naturally want to do

Thanks that makes since. I wounderd you know. Thankzzz