You can import an STL model or generate models using “Create Models” module in SlicerIGT extension, then move it around using a transform. You can use “Volume Reslice Driver” module to reslice the image along the tool axes to verify that the trajectory is feasible and safe. You may also use PathExplorer module to simulate a tool trajectory.
You may also find PortPlacement extension and PercutaneousApproachAnalysis extensions relevant. PortPlacement extension had a build error that I’ve pushed a fix for, we’ll see tomorrow if the fix worked. PercutaneousApproachAnalysis needs some updates for Python3.