sperber(a)informatik.uni-tuebingen.de (Michael Sperber [Mr. Preprocessor]) writes: It doesn't, but: - Custom will tell the user that the variable has changed outside customize when he tries to customize it. This may confuse the user. - When the user saves the variable, it will overwrite the value from the startup code. Not add to it. This means he will be bound to a specific location for the XEmacs distribution. In general, my advice is to split such user options in two. One for the standard (computed or large default) part, and one for the user specified part. It would be possible to extent custom so it could append or prepend to lists, instead of overwriting them. But the price would be a significant increase in complexity of the package. Now, how many here thinks they understand custom with the current level of comlexity? I find it hard, and I wrote it. Even without custom, I think it is a good thing if users in general can make customizations with `setq' alone, and not have to learn (and understand) advanced concepts (to a non programmer) like `add-to-list' or `push'. So user options should in general be overwritable.