I am surprised that if the Toolset fields appear in all widgets of Elementor but not in the specific Star Rating one it would be a Toolset issue 🙂
Elementor has created that Widget, and as well the dynamic Fields integration into those Widgets was done by Elementor Developers.
Toolset did add the Widgets of Toolset for Elementor, speak, our Toolset Views and Forms widgets, but not the dynamic input support.
You can make a very simple test:
Register a Custom Field with any other tool (WordPress core features, custom code, or a plugin) and check if the Star Rating Widget of Elementor does show the fields.
If it does it's because Elementor added specific support for that field (or tool you use) for that particular widget.
I've taken the time and made those tests and created several fields with different tools.
- ACF Field, which I then was able to see in the Elementor Star Rating widget, which means they have added support for ACF in that Widget.
- Simple Custom Field with core WordPress features, which does not appear in the Widget.
- Simple Custom Post Type Custom Field Plugin (hidden link), which does not appear in the Widget.
It should hence be safe to say, that for those Custom Fields to appear in the Star Rating Widget, a specific support for it needs to be added in Elementor's Code base, as the test above shows.
You can do that test on your site as well by activating Custom Fields in the single post you edit (in WordPress that's done with the "Screen Options" if you use classic editor or the cog/wheel and then > options > custom fields if you use Gutenberg) or using the plugins I suggested, they are free.
We are open to collaboration with Elementor, our contacts are established (by direct email to) and if any help is required we are ready to assist immediately.
However Toolset Custom Fields are just native WordPress meta, the only special to know is that we prefix the meta key with "wpcf-".
That is the sole difference to a native WordPress Custom Field - which, as seen above, as well does not work with that widget's dynamic input.
Note, I am not trying to pass the ball to someone else, I would be more than happy to solve this in Toolset, but we can't.
It needs to be done in Elementor's code base, as seen in the several examples above.
Thanks!