Built-in, Provided to animators, Ghost / onion skin with multiple options

Built-in ghosting / onion skin tools (3 stars are important, there are currently good alternatives, but this should really be an internal function)

A good alternative blendermarket.com/products/onion-skin-tools

• Ghost / onion skin (low overhead) that does not significantly affect memory and performance
• Can be displayed in front-to-back range (can confuse viewports but is sometimes required)
• A fixed one can be created for a certain frame (the frame should be recorded and automatically updated after the animation is modified)
• Provide a button to snapshot the object at the current frame and create a deformed model.(Additional features, extensions of the above, are usually useless, but useful when animators want to create some stylized ghosting)