The advice
mechanism is a bit like having hooks for any arbitrary function, but here you have actual hooks you can use, as well as a function argument which addresses your requirement directly.
So you can:
(a) Pass the function any arbitrary output filename.
(b) Use the provided markdown-before-export-hook
to setq whichever variables you need to (which at a glance looks like output-file
, output-buffer
, and output-buffer-name
).