Your form had a single button, and set p_eventtab2=_qtoolbar_etab2. If it walks like a duck, and quacks like a duck, etc., etc.. ;-)
Maybe you meant to post something else?
In any case, if you really want to make it a tool-window, then you should set p_eventtab2=_toolwindow_etab2, and register it with:
#include "se/ui/toolwindow.sh"
...
int flags = 0;
DockAreaPos preferredArea = DOCKAREAPOS_NONE;
tw_register_form('mytoolbar1', flags, preferredArea);
Also, your _image "button" initially sets p_visible=false, so there will be nothing visible when the window is shown. Anyway, there you go.
++rodney