It may happen that Tangents (if enabled) can be hardly seen in CIE windows. This depends on the fact that a measurement point is selected. The tangents, in CIE drawings are outlined in white only for the selected measurement. As a solution, to see all of them, I unselect the point (i.e. using the manual measure sliders pointing to a not measured point).
The same rule does not apply to 3D graphics, where all the tangents are always shown, regardless the point selection,

This is shown in the below screenshot combination. Above, as I was coming from built-in characterisation, the manual measure sliders are pointing at the black level. The only way to see all the tangents is by moving them (below part)


Steve, let me know, if you prefer I rewrite this post on Tip and Trick, based on my solution.
If you like, as WIBNIs I would propose to emphasize the selected tangent with a yellow line for the selected tangent and having a white colour for all of them for both 1D and 3D graphs. Also for that, please, let me know what you think about.

Yes, that is all as expected, and is designed that way.
The User Guides do explain the operation.

https://lightillusion.com/advanced_operation.html#graphs

CIE Graphs
The Tangent Lines in the CIE graphs show the direction and numerical xy or uv value of any error. Double clicking any point will select the given point, updating the Manual Measure window data, and enable the pop-up Point Info dialogue window. Additionally, direct point editing is available in higher ColourSpace license levels.

The selected point is indicated by a white surround circle within the 2D CIE graphs, and by a cross within the 3D graphs.
Note: when a single point is selected, all other Tangent lines will be dimmed. Setting a colour patch that has not been measured will make all Tangent lines bright.
Hint - move one of the Manual Measure sliders by one value...

Steve

Ya, I have read that, but in the user manual (https://lightillusion.com/colourspace_manual.html#graph-options). Generally applicable to tangents, but for 3D graphs it works in a different way, much more trivial, so an explanation may not be needed


But CS dimming makes tangent practically invisible in specific CIE triangle areas. Have a look:


I am sure it can be easily improved (Possible candidate for a WIBNI?).