Working side to side with Cuis, SqueakLightII and MinimalMorphic I found:

SystemOrganization classifyAll: #(#PluggableTabButtonMorph #DropDownChoiceMorph #LedTimerMorph #TickIndicatorMorph  #SimpleSwitchMorph #DumberMenuMorph #PluggableMultiColumnListMorphByItem #FloatingBookControlsMorph #BasicButton #PianoRollScoreMorph #ListComponent #EToyProjectDetailsMorph #StringButtonMorph #CircleMorph  #ScaleMorph  #FunctionComponent #PrintComponent #SquishedNameMorph #FlexMorph #ClickExerciser #TransitionMorph) under: 'Morphic-NotInCuis'.

(MCPackage named: 'Morphic-NotInCuis') unload.

So what’s the criteria?

Morph allSubclasses in all.
List of classes with allCallsOn size = 0 and allSubclasses size = 0
And manual select some sure at some time you need.

Anyway, both SqueakLightII and MinimalMorphic could load classes from repository if need to

http://www.morphle.com/~edgar/LoadingSomeUnknow.mov

You know 3.10 don’t have .mp3 and .mpg play right ? And how you have this again ?

The .mov shows the pre-alpha of this, how drag and drop a .morph coming from any 3.8, 3.9 or 3.10 image and asking to reload “missed” classes from server.
No need of know nothing about Monticello or repositories...

Edgar