It should be possible to remove a node with the YAML decoration feature.

Reason:
With YAML decoration a developer should be able to modify definitions brought in by other modules to achieve the definition that they requrire. Without this feature, they can only add properties.

For example, it is not currently possible to remove a field or tab from a dialog, or remove a page or a component from an availability.

Allowing to remove and re-add a node (override) would also enable removing specific properties which is not currently possible, but should eventually be supported.

See docs describing the current limitation: https://documentation.magnolia-cms.com/display/DOCS/Definition+Decoration#Definitiondecoration-Overridingpropertiesandchangingsubitems

To Specify:
What syntax should be used to remove nodes?

The syntax could use the concept of an override borrowed from JCR extends mechanism which removes all of the properties and subnodes of a node.
https://documentation.magnolia-cms.com/display/DOCS/Configuration+management#Configurationmanagement-Overriding

Validation: https://wiki.magnolia-cms.com/display/PMTEAM/Decoration+improvements+LDV