Furniture, Wood and Cabinetry Finishing - Final sanding to smooth poly finish

I have refinished a table top and put a semigloss
polyurethane finish on top. Because of a few tiny
bubbles in the finish its not as smooth as I'd like.
Will a fine steel wool work without leaving any scratch
marks on the finish?
Also, thank you and others who give helpful, expert,
guidance. I have learned a lot as a beginner, and this
website has kept me from giving up, and helped me keep
moving forward with this project.

dlmcsm,
A fine steel wool, 0000, will remove small bubbles and dust 'nibs'. It will also remove some of the glossiness. If you feel it has removed too much, a car polish should bring some of it back. One other trick I have learned, if the final finish is not exactly the way you want it is to thin
another coat of poly 30 to 50 percent with mineral spirits.
It will go on smoother with less brush bubbles and dry quicker and not attract as much dust. It should be emphasized that steel wool should never be used for water based polys, only oil based.

Fewalt has a good idea with the thin coat as a final coat - one way I 'cheat on getting a dead smooth finish is to use an aerosol for the final coat - works like a charm, assuming the piece is sanded out properly before hand. I use 600 grit wet/dry paper for the final sanding.

I do disagree on using steel wool to level a surface, although I certainly understand your wanting to do as little as possible to the present surface. If you can fix it 'good enough' without applying a coat, it's worth the effort. The steel wool might work, and if it doesn't you've lost nothing but a little time. Be careful with the automotive polish, though. It might give you more of a shine than you want.