Hi folks.
A trick: if you need to jump back and forth between two distant locations, I suggest making a scene for each of these locations.
Don't forget that you can switch point of view, including changing scene in the middle of a move or drawing operation.
For example, you need to start a circle on a precise point in a very cluttered part of the model (lets call in "Part 1"). You will need to zoom in closely to be able to snap to the precise point that you want. But, the circumference bust be snapped to a point that is hundreds of meters away in another cluttered part (lets call it "Part 2").
Option 1:
1 - Zoom in on Part 1.
2 - Start the circle on the proper point.
3 - While the Circle Tool is still active, zoom out, pan, orbit, whatever to get Part 2 in view.
4 - Zoom in on part 2.
5 - Click to finish the circle.
If you need to do that only once, you have probably choosen the correct procedure.
However, if you need to add, for example, a serie of lines between two parts that are far apart from each other, it can become very tedious.
Option 2:
1 - Zoom, pan and orbit to set a usefull view for part 1.
2 - Create a scene (Scene 1, for example).
2 - Do the same for part 2. You will have a Scene 2.
3 - Click on the Scene 1 tab.
4 - Start a line.
5 - While the Line Tool is still active, click on the Scene 2 tab.
6 - Complete the line.
Repeat as many time as required.
When done, delete the scenes if they are not required anymore.
Just ideas.