You can clone with
HTTPS or Subversion.
The example from the docs:
"plugins": ['TeaserPlugin', 'LinkPlugin'],
Does not work in the frontend. I can paste as many plugins as I want to.
I think, it would even be a good thing, to hide the add Button for Plugins, if the placeholders limit has reached.
In my project’s 2.3.5 install, CMS_PLACEHOLDER_CONF does limit the user to only the plugin's specified and the number, but that the user can use the "Move to placeholder" menu to move plugins into places that they shouldn't be allowed to. Also, one can create arbitrary plugins and move them into a placeholder in excess of the destination placeholder’s limits.
So, in summary, Its the "Move to placeholder" function on the front end that doesn't respect the CMS_PLACEHOLDER_CONF configuration.
In the backend, the user can drag-and-drop essentially any plugin into any placeholder, despite any CMS_PLACEHOLDER_CONF settings.
fixes issue #1308