[%d %%] works fine in the classicUI. It shows the percentage the Dimmer is set to. In the basicUI there is nothing left of the percentage string. The Text and the slider are fine.
The value is even missing for simple switch elements.
I proposed a fix to add the value and until now I got a very mitigate feedback ! The result is considered ugly !
In case my proposal is not rejected, I could add the value for the dimmer too.
Wait and pray lol
You can also use a Setpoint in your sitemap instead of a Dimmer. With the min and max values you can even protect your precious plants from hazardous conditions.