Block default values

Since its now possible to set custom properties for Block objects, it would be useful to define default values.

I thinking specific for the kroki Server property.
We use a self hosted instance for information security reasons.
When used a kroki block with the current implementation, the server must be specified with each usage.

To reach the goal to render the data local (which is a security requirement for most users), it would be useful to define a default value in the Admin Interface or in a configuration file.
Draw.IO and Excalidraw are also usecases for this scenario.

Thank you :)