A child preset stores "nil" both for an override the user switched off and
for a per-variant column it inherits from its parent, and the loader filled
every nil from the parent. Whenever the parent preset sets Retract Before
Wipe or another override, switching it off lasted only until the next
restart, project open or newer cloud copy.
Mark the filament overrides on their option definition with
nil_means_disabled and make is_filament_extruder_override_key answer from
it. Preset::save and the project-embedded preset diff write such an option
with all its columns, and the loader keeps its nil columns while still
mapping them onto the parent's variants by name, so nil in one of these
keys can only mean "off". Every other nullable option keeps nil as
"inherit this column". The cloud diff only force-emits a disabled override
whose default is a real value.
Hanif Koh
7de85397a6