Does the tool support porting Keil projects?

There's no built-in importer such as with SW4STM32 or TrueSTUDIO projects. I believe there are some guides (not made by ST) for making Keil projects function with Eclipse and from there you would probably be able to make it work with STM32CubeIDE.

However, my recommendation is to transition to CubeIDE when you start a new project instead.