Drawing tools do not show up
Screencastify features drawing tools, like a pen and a mouse pointer focus tool in tab recording mode.
Drawing tools work on all regular web pages with tab recording.
Note, that they won't show up on special Chrome-internal pages like the Chrome web store, the new-tab page or inside extensions. They also don't support desktop recording mode.
There is currently no way for us to add support in these cases for technical reasons. That's because as a Chrome Extension, Screencastify is limited to the constrains imposed by the Chrome platform, which don't allow to draw arbitrarily on the screen.