Addendum, 13.03.2023, 16.30 Uhr:
There is an additional way to apply the star rating using "Custom list values" for the Field POPULARIMETER that let you choose your own unicode stars like ★ from a drop-down-box in the Tag Panel.
All you need is to add a new field to your Tag Panel like this (you can name it as you like, in this example it's called POPM):
This allows you to choose the stars for your selected tracks from the POPM drop down box in the Tag Panel:
If you prefer to enter the stars directly in the File List for every single track, you can also achieve that.
You need to add a column with the Value and Field %POPULARIMETER%
In the File List you can enter the amount of stars directly, like * for one star or ** for two stars.
Please be aware that only the usual * (Hex 0x2a, Dec 42, as directly available on your keyboard) will be automatically translated into the according rating number.
Other entered Unicode characters like ★ will not be automatically translated in Mp3tag!
Demo from File List * input:
