The trio led England's attack in the victory at Wembley on Thursday, but their link-up play lacked cohesion as Roy Hodgson's men stuttered to an uninspiring victory against 10 men thanks to Chris Smalling's late header.
England now get set to face Russia in their Euro 2016 opener a week on Saturday and Kane is unconcerned by the poor form the triumvirate displayed in their final warm-up, insisting they can combine to make a fine partnership.
"I don't think you can judge it on one performance. The understanding isn't just going to happen overnight," he said.
"We were asked to play together against Portugal and we won the game.
"Of course we would have wanted a few more chances and a few more shots at goal, but it's something we are still working on, so there is no reason for anyone to get too downhearted.
"It's a learning curve. These games were to prepare us for the Euros and I feel they have done that.
"We'll see what formation the manager picks against Russia and we will do our best."
Kane's night nearly ended prematurely following a high challenge from Bruno Alves after 35 minutes, with the defender's boot catching the Tottenham striker on the head - earning him a straight red card.
"It wasn't a great challenge," he added.
"I am happy I'm still here. I was lucky not to have a few stitches. I think he just caught me with the top of his boot rather than his studs so I got away with one."