I have installed the version 2.18.24 in QGIS and apparently the plugin 'Digitizing tools' does not include the feture 'add ring' but it was replaced by 'fill ring with a new feature'. However, somehow I cannot create this new feature neither. Case this would work... if I want a hole in the polygon, do I have to create a feature and then delete it? Do anyone have some information on that?
add ring tool is part of the
advanced digitizing toolbar, which is not a plugin but part of the default installation.
go to the menu
toolbars and the 1st one is the
advanced digitizing toolbar