Hi, first off the proper usage of both these options assumes that you do not have auto saves enabled. You can see this from ther field's function button or in Settings-Lists-List Mappings.

Unless you've ever added alt-delimiters there won't be any (the alt delimiter list is empty out of the box). You can check this in Settings-Lists-List Mappings-Advanced List Settings.

Typically Yate uses the multi value delimiter as the only delimiter (;;; by default). It also has the ability to define alternate or non standard delimiters to be used when decomposing lists. For example , & ; etc.

The Add to List function splits the text by the multi value delimiter and whatever alternate delimiters you have defined. Each resultant item gets added to the list. The Add to List Ignoring Alt Delimiters function as the name suggests, ignores alt delimiters and only uses the multi value delimiter when determining the splits.

"de", "von", etc. would not be alt delimiters (unless you manually added them as such).

You are correct, in that the adding is a merge (case insensitive) as opposed to a duplicate.

You can always view the entire list and manually edit it in Settings-Lists-Composers.

I'm actually a bit embarrassed because I know perfectly well what a delimiter is but my head was in Yate-land when I read "Ignoring Alt Delims". My brain immediately mis-fired & went to the list of exceptions that goes along with the action I mentioned that takes just the surname but sometime the "de" in "de Falla" along with it.

In my defence, beer may have been involved. 😆