It’s not clear to me why you “can’t see where you are specifying the two the start points from”. Please explain more and/or provide an example so I can help sort it out.
Do you mean that there is no live feedback of where the cursor is positioned, so you have to eyeball/guess where to click? That is typical of almost all tools in SketchUp: the workflow is to use inferences from pre-existing points and directions, starting with the origin and axes in a blank model, not to try to click absolute point coordinates in empty space. You can, for example, create guides at specified offsets from the axes or existing edges (tape measure tool) or at specified angles to the axes or existing edges (protractor tool) to get intersections at desired absolute points. Then use these intersections when you click to place baseline points. There should be no inaccuracy in these points if you type in the required measurements when creating the guides.
You can then draw an edge between those two points to serve as a baseline for the trilateration. For additional triangles you can either use the same baseline again, use a side of the first triangle as a baseline, or create a second baseline to start an independent triangle, depending on how you took your measurements.
I hope you don’t mean the guide points created by my trilateration tool, because the calculation of their positions is as accurate as computer math allows, probably microns on a typical size model. But the calculations are GIGO; if you don’t establish an accurate baseline, that will propagate through the trilateration.
Agreed, that’s why I created the extension. I suppose it was overlooked because SketchUp wasn’t originally conceived as a surveying tool and Trimble has alternatives for that in other parts of their suite.