The draw mask feature is not appearing in video inspector after I create a mask

First reset your preferences. Hold Opt-Cmd s as you launch the application. Obviously we don’t know why it’s not appearing. To help us tell us step by step exactly what you did and post screenshots of what you’re seeing where.

Please do as Tom asked and post a screenshot.

Maybe you have to disclose the Effects pane?

if you hover your cursor near the word Effects in the Inspector, you may see the word "Show" appear. Click it.

Do you have that clip selected in the timeline?

Could you please show what you’re seeing in the video inspector when the clip is selected in the timeline?

Opt-Cmd-S toggles the clip skimmer. It won't have anything to do with the draw mask. Maybe you selected the clip.