Key Commands are offered to Lengthen Durations by specific values. (eg. Lengthen Duration by dotted 16th note). But the menu items under Write → Edit Duration → only offer Lengthen/Shorten Duration by Grid Value, not by another specified value.
Are those menu items hidden somewhere else (that I can’t find) or are they only available via the chosen Key Command keystrokes? (Searching for shorten or lengthen only highlights those grid-related menu items).