besides snap to grid drawing tool option suggestion, another one I have is to add a library similar to autocad. I envision a place to draw and store a selection of shapes you can drop anywhere kind of like a widget. Also be able to move them around on the canvas like a widget, then edit it if you want to customize it onto the canvas or within the library. Hope that makes sense.
Not familiar with autocad, but it seems like what you are describing is close to how the "canvas" widget works, which is a drawing-area that can be moved like a windget.
https://beyondloom.com/decker/decker.html#canvases
If you have an image in the clipboard, you can make a new canvas based on it by using Edit → Paste as new Canvas. This makes it easy to create “paper cutouts” that conceal part of a card and are hidden or revealed by scripts. You can likewise copy the image from a selected canvas to the clipboard to manipulate elsewhere with the drawing tools.
If what you are looking for is closer to an "icon font" I have one in development here, that you are welcome to wish aditional icons for.
Ahh, so you are requesting a widget group that can be copied/pasted, I guess, this can be implemented as a widget library thing? (Pretty sure this is a huge project in itself, maybe can be a importable module, so as to not bloat vanilla decker) A work-around I suggest for now is shift-clicking all components of the desired group/elements and then pasting them elsewhere,btw can you provide more context as by canvas do you mean the workspace area of decker or do you mean the canvas widgets in particular?