Yes, it is possible to CNC milling stainless steel with complex features. It can be more challenging, though, than milling stainless steel with simple features. This is because intricate features require more specialized tools and precise machining. Here are some factors that can make CNC milling stainless steel with complex features more difficult:

• The complexity of the feature: It will be harder to machine a feature the more complex it is. This is because intricate features frequently call for several, extremely accurate passes of the cutting tool.
• The size of the feature: It will be harder to machine a feature the smaller it is. This is because chatter and vibration are more likely to affect small features, which can result in a subpar surface finish.
• The material of the feature: It can be more challenging to machine some materials than others. Complex features may be more challenging to mill in stainless steel than in other materials due to the material's relative difficulty to a machine.

Stainless steel with intricate features requires the use of specific tools and methods when CNC milling. To mill stainless steel, you'll need sharp-end mills made especially for this purpose, as well as an accurate and precise CNC machine. To keep the part from overheating, you might also need to apply lubricant or coolant.