For C++17 there is the library Cista, which borrows inspiration from Protobuf but without having to compile protocol buffers in an intermediate step. It features things like zero-copy and uses C++17 structured bindings to implement rudimentary reflection. This unfortunately requires significant code changes because you have to replace STL containers with ...
For C++11 I can recommend cereal. To some extent it even works as a drop-in replacement for Boost.Serialization with only minimal code changes. In my experience the documentation is pretty good and it is header-only. https://uscilab.github.io/cereal/
CudaText editor is not an IDE, but it supports plugins, and LSP Client plugin exists. With LSP plugin and LSP Server for C++ language, you will get partly what is needed.
Then CudaText can split single editor window to 2 parts (for the same file).
Menu "View / Split tab / Split vertically".