Not in cpp projects.
That's true. POIDE was written specifically for Pelles compiler... It's not a general purpose IDE at all.
There are a number of limitations to doing CPP on an IDE designed for a specific C99 compiler. Some we can compensate for, others we cannot. IDE specific functions such as Code completion, call tips, dependencies, etc. do not work in cpp projects. I wasn't even able to get it to add #includes to the project tree... but that's because we're leveraging a behaviour the IDE was never intended to produce. So it should not be unexpected.
My goal was to let you build some libraries and DLLs that use C++ internally as part of your C-99 projects. I certainly would not tackle a large multi-file C++ project in this setup. If you are doing a lot of C++ you would be further ahead to get
Code::Blocks or
Visual Studio... for resources you can use
ResEdit or one of it's clones.