Glyphs Catalina, Plugins and Modules, developer cannot be verified

I made a macOS Catalina Clean install, and freshly installed Glyphs.

As already under High Sierra the modules (Vanilla,…) can not installed, the beach ball spins without end, nothing happens.
Bought plugins: When starting glyphs, I get a warning: “… because the developer cannot be verified”

I have the following plugins: SuperTool, Show Stems Pro, Letterink

I believe you have outdated versions of the plug-ins. Delete SuperTool and reinstall it via Window > Plugin Manager.

For the Plugin Manager, I need Git-Kommandozeilen-Werkzeuge, which are not included in Glyphs:

Die Git-Kommandozeilen-Werkzeuge sind aktuell nicht installiert.

But, the link(s) are dead:

Can Vanilla also not be installed without GIT?

The first link works fine for me.

Wow, now the link works also for me. But now, by installing SuperTool, I get this message:

Could not install plugin.
Please check the write permissions in the Application Support folder and content the of plugin packages database.

Well, what next?

Just try again. This can happen when you install it the first time.