Attach multiple clangd clients to buffer

I am working on cpp projects that are organized according to the structure below:

├── proj1
│   ├── compile_commands.json
│   └── src
└── proj2
     ├── compile_commands.json
     └── src

When working on proj1 I would also like to gain access to symbols defined in proj2.
I tried to add proj2 to the current workspace folder, but without success.
Is there any strategy to achieve this result?