LuiHs, you can't partially import an IOC, it's a complete hardware setup. So it's everything or nothing.
If it's only for a few peripherals and pins, manually copying them won't take long, there aren't so many fields.
You can't open 2 iocs at the same time inside the IDE, but you can run standalone cubemx in one side and IDE-cubemx in the other, that way it's much easier.
You don't need to install cubemx, you can use the IDE's like this (MX version might be different):
java -jar c:\ST\STM32CubeIDE_1.7.0\STM32CubeIDE\plugins\com.st.stm32cube.common.mx_6.4.0.202111222105\STM32CubeMX.jar
Add that line to a script to quickly launch it and it'll be straight simple.
Actually, it has become a pretty good IDE. Had lots of issues, but it seems that they're finally fixing most of them.
Eclipse is being used by a lot chip makers, so in the end its a good idea to learn it.
The other day I installed MCUXpresso to compile something someone who couldn't... 99.99% the same, totally straighforward, and I had never used it.
No idea why so much hate against Eclipse, it's slower than Notepad, sure... but has tons of extremely useful features that save a lot of time. Code completion, mouse-over hints, references/declarations, real-time code analysis (So you don't need to compile to see the errors) and debugging, all in one...