Use letter-keys like modifiers combined with left-click on an individual Grease pencil stroke to trigger transform !

A cool use case demo by Daniel Martinez Lara is available on this link : https://www.youtube.com/watch?v=ino4Njemtds

G : Grab
R : Rotate
S : Scale
E : Pinch

Pinch is one of the most powerful of the tool to tweak drawings

Since first release, more tools have been added:

W: Slide

Shift + S (press): Smooth & resample

X (press): Delete

Alt + S : Thickness tweak

More infos on youtube video demo (not showcasing all features)

https://www.youtube.com/watch?v=HuVyzE6qmUY