>Still, kind of 'meh'. Because this way I cannot access the z-value...
You may use param3d() to plot a fake 3D polyline to support and "overlay" datatips.
Then the datatip will include Z by default.
If you are running 6.0: you may also try to use the new .display_components datatip field
https://help.scilab.org/docs/6.0.0/en_US/datatip_properties.html Never tried Z whether gca().view=="2d".
>Is there a way to align the text in the box (instead of centered)?
AFAIRemember, it used to be possible with the former datatip implementation up to 5.3 (or 5.4?).
But this feature has disappeared, as still a bunch of other graphic features, since 5.4.
Indeed, this compulsory centering is rather boring, to say few.