Great analogy!
+1 for bottom left.
I’ve been using the new interface for a few weeks, and after getting accustomed to the UI, I find it really nice for the most part. The icons are great with good contrast and the labels popping out when I hover the Pencil help reinforce my memory. I’ll turn that off in the future. I am right handed, use an iPad and Apple Pencil. About 75% of time, the iPad is connected to the Magic Keyboard, and the other time, just the iPad held with left hand. Almost always I have the Items side panel open which puts the tools out of thumb reach, so the Pencil is my method of selecting tools. That works for me. Kudos to the Shapr3d teams for the update and the five star presence on the forums to help customers.
Prior to the update I didn’t use the keyboard shortcuts very much because it was easier to keep my focus on the screen and tap tap with the Pencil to do what I wanted to do. I don’t want to put the pencil down and will often poke at the right hand side of the keyboard with the pencil while the left is hitting ⌘ ↑ or other left side keys. This works, but I’d rather not have to look down to hit P to project; so I’ll hit the (more …) icon and tap the P from there.
The search icon doesn’t do much for me, yet. I am hoping that at some time it will search and identify design item names and not just commands.
To import/export, the shortcut keys are useful. For me, these actions are (necessary) interruptions to sketching or modeling and the pencil goes to its rest on top of the iPad and I’ll use my finger for selecting, and type with both hands or use the on screen keyboard.
The icons at the top, with the exception of undo/redo are used only on occasion. And this top set of icons is different. They do not get the labels popping out when hovering the Pencil, which if fine, but they are different. And the undo/redo pair really seem out of place.
I have changed my habits. When using iPad with keyboard, now I’ll use ⌘ Z to undo (with the old UI this was pencil tap). That is ok. When I’m not using a keyboard, I still want to sweep to the lower left with my pencil then interrupt my workflow to hit undo/redo. When I finally hit the target, I have waved my arm over my work and lose visual focus to watch the undo (or several undo’s) to look at the design to see the details. (Interference etc.)
I agree with many who have voiced their Lower Left preference for the undo and redo icons.
Over the years, I’ve appreciated the regular updates to Shapr3d and look forward to see how it evolves.