Hi,
you need to check NX_ROOT\site\mods\www\wwwroot\scripts\std_head.js file, which generate SDM logo so you can modify it adding URL into it.
I'm using this js function to navigate to main form:
upd_specific_frame('sd','DISPLAY_FORM','HTMPL=bin_form_np.htmpl')
upd_specific_frame('sd','DISPLAY_FORM','HTMPL=home.htmpl')
Regards.