If you import electrode model into segmentation then you can see the name of the electrode in the Data Probe window (lower-left corner) when you move the crosshair over it (Shift+MouseMove). You could do the same in 3D view with a short script (see example script in this topic). You could also write a short script for highlighting the segment in all views (temporarily changing its override color in the display node) and displaying the text next to it (by adding a temporary markups fiducial node and set its label to the name of the segment).
You can enable projection and the same distance-encoded coloring for model nodes: Models module / Display / Mode → Distance encoded projection. By editing the color table, you can set arbitrary fadeout and/or color change behavior.
Line/plane intersection position is a very simple computation and once you have that position, you can see if it is in the slice view’s region (something like this: transform it to the slice’s coordinate system by applying inv(XYToRAS) transform and see if its XY coordinates are within FieldOfView size and Z is within slice thickness).
This would be useful as a general solution, and I think VTK hardware pickers (e.g., vtkPropPicker) provide this. SEEG case is a simple special case, as electrodes can be modeled as points or cylinders (lines), so it is trivial to compute intersection position with a plane.