Sometimes it is much easier to create your shapes by cutting and joining existing shapes.
To do this, I use the Area objects in HeeksCAD.
For example, if I have a shape like this:
and I want to make the shape which is the circle with the rectangles subtracted from it.
I can right click on each item in the Objects window and choose "Convert to Area"
So, I get 3 Area objects. Then select all three Area objects, using the Ctrl key to select multiple objects. Make sure to select the circle area first. Then right click and choose "Cut Areas"
You then get the shape you want.
You probably want to turn it back into a sketch, by right clicking on the area and choosing "Make to Sketch" ( you need to click on the Objects window before the sketch appears for some reason. ) You can then delete the Area object.
The shapes must be closed to work.
With this shape:
I cut the inside circle from the outside.
Then I cut the other circles from the outside.
Then I intersected the triangle with what was left.
This is the result:
