Cannot control "what" text does

In Musescore 3 I had created custom dynamic symbols such as mf- mf+ etc, to change the velocity to values in between the ones that come in Musescore original dynamics. Using the inspector I could select the dynamics text and specify its velocity number and that affected the playback.
Now in Musescore 4 I was able to edit the text of dynamics however I want, like p+, p-, pp+ etc. But when I go to properties I find all the properties related to the appearance of the text, but none related to its effect on playback.
Digging a little deeper, I found in properties a beautiful menu that allows me to specify what kind of text it is, tempo, dynamics, staff etc. It has much more options than MS3 had, even user defined categories. But no matter what kind of text I choose, the only properties I can change are related to the appearance of the text. I could not find any way to control what a text does to playback. I need to customize dynamics text with custom velocities. And I would like to customize the effect of other categories of text too, but I can't. I would start using MS4 right now, but I couldn't.
How can I create custom dynamics with custom velocities? And how can I customize the action of other kinds of text? (If there are no option for this in MS4 GUI, I accept hints of how to do it customizing some xml file, some palette file or anything like that. I was used to do so in MS3.) Thanks.