Nabi took 4 for 9 as Hong Kong fell away to 122 all out, but it was Raees Ahmadzi who took the Man-of-the-Match award for the second consecutive game.
Kabir Khan, Afghanistan's coach, has genuine belief that his team are good enough to play in the 2011 World Cup.
"2011 is a dream - I am very hopeful about it," he said. "I want the players to be there as they really deserve to be. We are taking things as they come and obviously we have to go through Division 3 to start with. Once we have achieved that target we will be through to the World Cup Qualifier and we will make another plan for that."
Khan has already begun planning for Division 3 in Argentina in January 2009, which is a six-team event involving the two qualifiers from this event, plus Papua New Guinea, Cayman Islands, Argentina and Uganda.
"We have time on our side now. The guys have already started playing as a team. We need to raise our game a bit and be a bit fitter and be more mentally prepared for the tournament," Khan said.
"We have options for our training camp. We could go to Pakistan or India. I would prefer to have a training camp with similar conditions to Argentina. If we have a camp in Afghanistan or Peshawar it will be winter and it will be cold, while the weather in Argentina will be warm."
Hong Kong coach Aftab Habib was delighted with his team's performance despite the final defeat. Zain Abbas, Hussain Butt and Tabarak Dar have been in excellent form all week and Habib thinks his side have the ability to compete at a higher level.
"I don't want to look too far ahead but it is a dream for me and it is a dream for a lot of our players. Our next main aim is to do well in Division 3," Habib said. "It is an achievable dream and it is just a matter of putting in a lot of hard work. Everything is achievable. I think we are getting better and better every time we play. Coming here early has really helped us and I know we can go forward.
"The boys have to keep working hard at their skills and their fitness, as the higher level you go you obviously have to be a lot fitter as well."
In the final, which is used for ranking purposes, batting first on a turning track, Afghanistan made 179 all out. Ahmadzi (49) and Nowroz Mangal (40) put on a vital partnership of 66 for the fifth wicket. Nizakat Khan (4-29), a 16-year-old legspinner, showed great maturity in dismissing Afghanistan's lower order.
In reply, Hong Kong started strongly but quickly fell away as Nabi once again showcased his spinning talent. Hamid Hassan almost finished the final in grand style with a hat-trick, but he overstepped when bowling a pinpoint yorker.
In the third/fourth play-off, Italy defeated Tanzania by 70 runs at University, while Fiji secured fifth place with a 27-run win over Jersey.
Cassim Suliman, ICC's regional development manager for Africa, paid tribute to the work of the Tanzania Cricket Association in the organisation of the week-long tournament.
"[They] have done an excellent job in staging the World Cricket League Division 4, which provides an important opportunity for sides from across the world to gain a pathway to the World Cup and play competitive cricket in a global structure," he said
"Tanzania's young players, many of whom have come into the game as a result of the excellent schools programme, have gained invaluable experience of playing against experienced cricketers and I am sure that this will help them improve in the future."