Some ideas I would like

1. Fill with a transparent color, I want to make something like a window but with a solid outline and using the ruler tool after tracing something like a highlighter or a transparent mark is too hard, so maybe have that option 

2. More ruler presets: we should be able to trace other shapes like a triangle for an option maybe under the circle tab idk

2.1: speaking of rulers, you should be able to use lasso select in a shape like the rulers

3. Blur effects if possible we need Blur effects for like smear frames or something

4. Custom shapes for pens, you should be able to change between like a circle brush or a diamond brush