Using Quick Add by specifying the capitalised letters associates the combination you entered with the Transformer chosen. e.g. entering 'AC' and selecting AngularityCalculator, will select that Transformer in the list next time you enter 'AC'.
But I don't use the AngularityCalculator often, so next time I use 'AC' to find the AttributeCreator I have to go scrolling for it in the list. It could be nice if they were grouped together so FME remembered all the 'AC' typed/selected transformers and grouped them together, then listed the remaining Transformers after. Maybe an FME Option to reset/edit the list or toggle this mode with the existing mode.
Of course I could use my own shortcodes such as 'CA' for AngularityCalculator but that's harder to remember!

