Only If My_Project/ is the sketchbook folder. Libraries must be installed under the libraries subfolder of the Arduino sketchbook folder. Unlike sketches, the sketchbook folder does have technical significance for libraries.
If RobotConfig.h provides the code you want to include in your sketch, and that file is present in a library installed under the libraries subfolder of the sketchbook folder.
The first thing to understand is that creating a library is not some onerous task. You only need to create a folder under the libraries subfolder of the sketchbook folder and move your header file into that folder:
<sketchbook location>/
├── libraries/
│ └── RobotConfig/
│ ├── RobotConfig.h
... ...
A .cpp file is not required. Although it is best practices to give the header file and the library folder the same names, this is not absolutely mandatory.
You can put the library code files under the src subfolder of the library (the "1.5 Arduino library format") if you like, but if you do that you must also add a library.properties metadata file to the library if you choose to do that. If you instead put the code files in the root of the library folder (as shown in the diagram above), then the metadata file is not required and the library can consist of as little as a single header file.
So the effort required to make a library like this is utterly trivial and not worth considering as "overhead".
The main drawback of using a library as compared to just putting a copy of the file in each sketch is that the library approach is more complex. If you want to back up or distribute your project, you must remember the library dependency in addition to the sketches.
The drawback of putting a copy of the file in each sketch as compared to using a library is that you will need to maintain two copies of the same code.
So I think the "worth it" determination will depend on how often/likely the content of the header file will need to be modified over time.