While the Nazis had the goal of uniting the German speaking peoples into one nation, which included the German speaking Swiss, they did not invade Switzerland during the war for several reasons.

1.) Invading Switzerland would be an operational nightmare. The terrain is very mountainous and access for vehicles in many areas is limited to narrow passes and valleys. Defending is always easier generally than attaching, and these conditions greatly improve the position of the defender, while reducing the advantage the Wehrmacht had in armour and numbers. Further, Switzerland has an extensive network of field defences and national service, which would further make any attempt at invasion difficult. To conquer Switzerland would be an incredibly difficult and costly campaign, and be a large waste of resources which they could ill afford to waste.

2.) Switzerland was useful to some extent as an independent country, as a neutral state it could be used as a diplomatic and financial hub by Nazis Germany.

3.) The Swiss has declared themselves neutral, and invading yet further neutral countries (beyond those already invaded) would possibly lead to worsening relations and possibly war with other neutral states which took exception to attack on the Swiss.

4.) The Swiss would not capitulate easily, and given the operational conditions which an invasion would bring, the campaign would be incredibly bloody and many would likely die. This would be terrible optics in terms of propaganda, Germans would be killing ‘Germans’ (Swiss), and this would appear contradictory to Völkisch thought.

5.) The most important reason is largely because considering these issues, it wasn't worth the effort. Generally, while depraved and only understandable within the Nazi worldview, decision making would only tend to result in the invasion of states when it was thought it would be to their benefit.To that end, the Nazis generally would attack a state with a particular goal in mind, and in accordance with ideology and strategy. For example, invading the Low Countries in May 1940 allowed the Wehrmacht to attack a weak point on France's northeastern flank, while attacking the Danes and Norwegians in April 1940 allowed the Kriegsmarine to gain naval bases which threatened Britain in the North Sea, while also disrupting British operations and supply routes. We can see a similar point with Sweden, which unlike its Scandinavian neighbours was not invaded. Not because it couldn’t be done, but because it wasn’t necessary.

So essentially, while occupying Switzerland offered some positives to the regime, these were all things considered not worth the costs they would incur.