grough

Thank you all. My initial failure to understand how keyboard shortcuts are configured was holding me back. I've now set up a few shortcuts based on your suggestions, and my problem is solved.
Right, it makes sense to rotate the Artboard instead of the view. I have mapped Control-L to Layer -> Transform -> Rotate left
 
I have also mapped Control-Shift-L to View -> Rotate Left and indeed it is much faster than clicking the menu.
 
That's a clever trick I will keep in mind
 
Very cool, setting up two views works perfectly for this purpose.
I have just started learning Affinity Designer 2. You have all given me very helpful information today. Thank you!

Thank you all. My initial failure to understand how keyboard shortcuts are configured was holding me back. I've now set up a few shortcuts based on your suggestions, and my problem is solved.
Right, it makes sense to rotate the Artboard instead of the view. I have mapped Control-L to Layer -> Transform -> Rotate left
 
I have also mapped Control-Shift-L to View -> Rotate Left and indeed it is much faster than clicking the menu.
 
That's a clever trick I will keep in mind
 
Very cool, setting up two views works perfectly for this purpose.
I have just started learning Affinity Designer 2. You have all given me very helpful information today. Thank you!

Another option is to have two views.
Open your document Select View > New View In the New View tab rotate the document -90º using the menu option View > Rotate Left or the using the assigned shortcut keys, for me that would be ^L (Ctrl + L)  That's it, you now have two tabs open, one with the document as it opens initially, and one document view rotated -90º you can simply click on the tab to see the view. What you do in one window will be reflected in the other. On Mac you can switch between the two views using the keyboard shortcut Cmd + ` not sure what it would be on windows but I'm guessing Ctrl + `
On Mac, the ` key also has the tilde symbol ~ on it

Is it just for checking? (rotate, check, and return)
Try OS rotate screen (Windows Ctrl+Alt+Left arrow, and Ctrl+Alt+Up arrow). 

Assign a keyboard shortcut, you still have to use the shortcut 6 times but you are only holding one key down and pressing the other six times so at least it's quicker.

I don't think there is a command for rotate document view by 90°.
But if using an Artboard, you can select the Artboard in the layers panel and use Layer > Transform > Rotate Left
You can assign a shortcut to this and to Layer > Transform > Rotate Right  to quickly switch between a portrait and landscape view of your document

Thank you all. My initial failure to understand how keyboard shortcuts are configured was holding me back. I've now set up a few shortcuts based on your suggestions, and my problem is solved.
Right, it makes sense to rotate the Artboard instead of the view. I have mapped Control-L to Layer -> Transform -> Rotate left
 
I have also mapped Control-Shift-L to View -> Rotate Left and indeed it is much faster than clicking the menu.
 
That's a clever trick I will keep in mind
 
Very cool, setting up two views works perfectly for this purpose.
I have just started learning Affinity Designer 2. You have all given me very helpful information today. Thank you!