"I'm trying to find a way an easy way to draw a slanted cone based on the known radius of the base, a known height, and a known vertical and horizontal angle at which I'd like the cone to lean."
A forum post for which we definitely do not need a plugin but can be done in a couple of very easy steps. In this tutorial, we shall follow some very basic tips how to enter exact dimensions and how to move vertices snapping to guide lines.
Start drawing the base of your cone. When drawing the circle (either before or after you clicked to finish it) type the value for the Radius. You can also type the diameter followed by /2 - then press Enter.
Now select the Protractor tool, first click to the origin of the circle then somewhere on the blue axis, start turning the tool, enter the Angle (here 15 degrees) and press Enter. A guide line will be created.
Now draw a line along the blue axis from the origin again. Either before or after you click to finish the line, type the Length (here 500 cm) and press Enter.
Using this vertical line, finish a triangle and use the Follow me tool to lathe a cone as shown in the second version of how to draw a cone ("Drawing a cone using the Follow-Me tool") in this Help Center Article.
When done, make sure that no geometry is selected and select the Move tool. Carefully hover over the top vertex of the cone until you get the "Endpoint" inference. Now click with the Move tool to grab the tip of the cone and start moving it towards the guide line. In my case that direction is along the red axis (shown by the red inferencing line). To make sure you keep on this line (or in any direction you successfully started to move along), you can press the Shift key - or in case it's an axis (like now) press the Right arrow key for the red, Left arrow key for the green or the Up/Down arrow key for the blue axis to lock the direction.
Snap to the Guide line and click to finish your moving operation.