and thanks for explanations.

Finally, this method does not store objects, and indeed, I can't imagine how that would work, as objects are dynamic references to the document. Instead, store the address or the contents of the cell (or both). If it seems like your project needs something different, maybe it would help to explain why you want to store an actual cell object, or how you expect that would work.

Cell was just as example, to represent an object. In fact, i was trying to record some object i create from a type i had defined.

public type ingredient
nom as string
feuille as object
plages() as object
methodes() as variant
.....
end type

So, i wanted to store somewhere this object created with some kind of instruction:
dim aliment as object : aliment = Ingredient.createNew(evt)
just to avoid recalculating the object's properties every time I need to access it. It's not to gain few hundred milliseconds, but just for the principle, ... And as it seemed to me practical to store dozens of ingredients to "have them at hand".
Maybe i should try another approach, like serialization ?

So, if userdefinedproperties is not adapted to my needs, and i guess globalscopes is not too, is there a way to record objects ? (at the reflexion, is not inconvenient if an object is stored in the document and persists after closing libreoffice, but , objects can be stored ...)