However, you could use these options, depending on the context:
* Gen. (short for general)
* G. (short for general)
* Multi-skilled
* Polymath
* Broadly skilled
It's important to note that these are not official abbreviations, but rather informal ways to represent the concept of a generalist.
Ultimately, the best way to communicate your meaning is to use the full word "generalist" or provide a brief description of their expertise.