Hey Ali, Take a look at the parameter set in the NestML Github repo, often you can find more information that isn't found in the documentation.
Specifically, for `static_synapse` models, there is a parameter `d` that may be what you're looking for regarding axonal delays.
NestML code for `static_synapse`: https://github.com/nest/nestml/blob/003d17a6425c3f8d88ed3aedd8d8e1d76245966e...
Cheers, Anthony