"grace notes after" are not supported
There are numerous issues about one or the other aspect of this lack (see below). They all would be fixed with a proper implementation of "grace notes after". At the moment there is only one lonesome icon without any code behind.
The implementation is not very easy because the concept of grace notes is not friendly to the idea of grace notes after, but ist is quite nessessary. There are not many scores written between 1770 and 1950, that do not need "grace notes after". The substitution with "grace notes before" to the next note is unsatisfactory if you want to bind the grace note to the main note by a slur. To add "grace notes after" to the last note of a maesure is nearly impossible (I know, there is a workaround, but it is not reasonable for practical use).
If a XML score containes grace notes at the end of a measure, the import causes bad errors. If there is only one voice, those grace notes are completely lost. If a stave has two voices and the first voice has grace notes at the end of a measure, the grace notes appear totally displaced: they are added to the first note of the next voice at beginning of the measure (because they are understood as "grace notes before" and added to the note, that is the "next" one, not in the order of music but in the order of the import algorithm).
The other issues concerning the problem are #19154: Grace: 8th after applies appoggiatura, #21822: Grace note after note appears as appoggiatura, #22187: grace notes AFTER the main note, #11780: One kind of grace note in palette, #24520: Grace Note: Grace 8th after does inputs as forward Grace Note,#15022: Grace after notes wrongly aligned, #19426: Grace note at end of measure imported incorrectly.