Hoping for

I have a simple implementation of annotation (..etc) in mind, but I need a way to control zathura externally. For example, I hope the following scrolls the document

[me@laptop] $ zathura --instance=<ID> --command="sc_scroll"

where, sc_scroll is the built-in function that scrolls the document.

Question

How to send commands to zathura externally?

As a quick note, sc_scroll calls position_set at the end of itself. sc_scroll then calls refresh_view(zathura) in its end. Then refresh_view calls

  g_signal_emit(zathura->ui.session->gtk.view, zathura->signals.refresh_view,
                0, zathura);

which finally communicates with an external packages.