Hi Paulo.
I had a look at the problem to see what happens:
1) I made a new class test project, compiled it to a library.
Made a second project loading the library and adding the CustomView in the Designer worked.
So this shows that B4A version 4.30 works OK with a new project.
2) Then I made a new project for yor custom view, added a new class module, copied the whole code of your class into it and compiled it to a new library.
Made a new project, tryes to add the CustomView in the Designer, no success, it doesn't appear.
Then I saw in this class that the Public Sub DesignerCreateView(Base As Panel, lbl As Label, Props As Map) line was underlined with a warning.
3) Then I made once again a new project at the beginning only the skeleton and where I wrote a new Public Sub DesignerCreateView(Base As Panel, lbl As Label, Props As Map) not copying from the other project.
Compiled to a new library.
Made another new project to test the library and the CustomView appears ?!
Copied the rest of the code into the class, comiled the library and it works.
So, I don't understand why this happens.
I think that Erel should have a look at this.
Because I have also libraries where the CustomView appears in the Designer and other libraries where it doesn't appear.
Attached the two last working projects and the library files.