Summary

I got tired of reinventing the wheel everytime I wanted to make a countersunk screw hole in a Tinkercad project. I know some of the advanced CAD programs have built-in screw profiles, but my go-to program does not. The attached STL file is an accurate profile for standard metric countersunk screws, sizes M2, M2.5, M3, M4, M5 & M6. The shanks are common clearance diameters, and the countersink angles are all 90-deg.
Rev: Someone asked for individual STL files, so here they are, numbered M2 thru M6....

To use:
-import STL into Tinkercad or similar program
-select & delete unwanted profiles
-turn needed profile into a hole and place into project
-if you need a longer depth, duplicate the profile, blank out the countersunk head, then extend the shank to what you need and put it on top of the existing profile and merge
If you need larger sizes, find out what the countersink diameter is, then select the nearest profile size, hold down shift while moving one of the corner boxes in or out until close to the desired diameter. The remaining screw dimensions will change proportionally.