Crop to reorientate has been such a Godsend in my workflow, that I've set up C as a shortkey to reset rotation in pretty much any program that will allow me to do it.
Ugh same, I cannot live without expresskeys anymore. I'm also lucky to have one of the older Cintiq models that still had the expresskey build into the device itself. I'm so sued to them by now, that when I start working in a new company one of the first things I do is import my wacom settings to the worktablet haha.
Same, I'm completely wed to the cintiq + EK remote. I've thought about moving to an iPad pro but I can't imagine lifting my pen off to use gestures like a savage. 
I bought an ipad pro and I barely use it.
The feeling of the pen on my xpen 22e is so much better than the apple pencil
on the ipad. I had a Wacom companion some years ago and the ipad is much worse
I literally spin my canvass around. I use a Dell Inspiron 16 (it's a 2-in-1 with a fantastic screen) for drawing , and I fold it up as a tablet, select "rotation lock", and then flip it all over the place as I'm drawing
The invincible comic used to use the same pic a few times to add some emphasis to scenes or show thinking. I always thought it was pretty clever
I don't take many shortcuts simply because I love the hand drawn feel however for buildings I draw them once and insert the image of the building into any bus I can use it for
I like doing animation style panels especially in conversations. Body language is a huge part of a characters personality.
The shortcut is now I can reuse backgrounds multiple times.
If it works it works right 
I can respect that. There is something about the act of creating itself that just feels so satisfying to do.
I love this, now yor panels aren't just part of a comic book anymore, they have become animation keyframes!
That's one thing that helped me to determine the poses in panels, I started to treat them like the keyframes of animation.
I copy and paste my backgrounds when possible 
I also make then very blurry when they aren’t important, so you don’t focus on them and I don’t have to put details in 
Also using multiply layers for shadows helps a lot.
I'm just now learning to reuse backgrounds; it saves SO MUCH TIME!
Wish I thought of that before
Also I have a face/personality set burned into my memory. I don't have to always try to come up with every detail of a character because of personality types and how each has a matching face to go with it. Less thinking, more OC!
I used to write down every single step of what I wrote, but after a lot of work... and I mean a lot. I can mostly do all the pre-planning for a writing gig in my head. I only write it down if the job asks for it.
I had a set of head poses for the head to the side, to the front, and facing some other direction, so I could copy/paste one of those heads into any scene and draw the face onto it.
I guess you might call it a shortcut that I occasionally skip the line art and just do my drawing in color from start to finish.
I have too many to even start listing them. Everything from ignoring hair in roughs (block it in then finish in the inks), to drawing certain hand poses. The one that saves the most time is shading. Color everything with flats to the colors wanted. Create a layer above that layer and call it shadows. Block off the area that are in shadow and fill with dark blue (almost black, but never use black.) Then just slide the opacity down to 70-80% depending on the deepness of the shadow. Instant true shadow color. 
All of the shadows were created this way. Takes minutes and you don't have to remember your color theory classes to figure it out.
If I have something I know I'm going to see a lot. This example being Venetian blinds I'll take the time time to make a full page of it and from then on I'll just paste it in.
I make preset iris's in both black white ( for manga ) and fully coloured in different eye colours ( for illustrations ).
This way I can just import an iris design into the picture / comic and set it up accordingly. Saves time for me.
I'm lazy at shading evenly and will often do a light layer of graphite and then smudge it with my finger. it might be wrong but Mark Crilley did it, so it works for me lol.
I like going straight from story boarding to lineart. Saves a LOT of time. It gets a bit complicated for more complex panels, but oh well
I've since developed another short cut, which also helps cover up a physical limitation of mine and, in my opinion, looks better. I used to do several sketch layers in different colours and refine the drawing with each layer until I was happy with it, then I'd do ink in black.
Now I simply do my final sketch layer in black and call it my ink layer. I will still usually refine some things during colouring, but for the most part it goes straight from final sketch to colour. The resulting drawing has a wilder, rougher look, but to me it looks better, and it covers up the fact that I have very shaky hands and struggle drawing smooth lines. Cutting that final "smooth" ink layer saves a lot of time, a lot of aggravation, and produces a nicer drawing.
Here's a drawing of Daecon done in my old style, with the "smooth" ink
And here he is in the new style, with "rough" ink:
