My thoughts are that this is some very interesting work. Do I understand correctly that your idea is to create (pretty advanced) guides on-canvas depending on the select symmetry, and use those to define the base tile? And then you want to be able to differentiate between "exterior" tiles and "interior" tiles, with the "exterior" tiles tiling only so much that they form a one-tile thick border around the tiles?

Exactly! Of course, you can toggle on and off whether to delete tile "exteriors"  for non-edge tiles. The "delete tile exterior" is mostly for the advanced  seamless designs, not if you just want to toss around a few bubbles.

Have you thought about the interaction with things like random displacements (and non-constant displacements).

I admit I haven't thought that far... I'm not an expert in tilings, and even  less in tiling algorithms, so I've never thought beyond "this connected to that." I guess it's possible, there are two separate options you can tick after all: - Make seamless tile - Exclude tile exterior as needed

So, you could in theory tick the second box, and Inkscape will cut out  the edges but still apply all the position and size transformations as  needed. So the result doesn't need to be seamless.

Have you seen this java applet - designed to explore penrose tilings.  Its not guide based in the same way as yours but instead you manipulate  exemplars and see the result. You can see the interdependence and how  your guides might correspond to edges on these tiles. Not sure if useful to you or not ? http://www.cgl.uwaterloo.ca/~csk/software/penrose/

Thanks a lot for the link! That's actually a really good reference for how  "guide points" are supposed to look (though... the tiles are different).  In my version you can also create a guide point and drag out a segment, the both of which show up in other relevant sides.

The idea is that they help create absolutely smooth transitions: just create  a node on the guide point, and snap the node's handle to the edge of the segment guide. Repeat with the node's counterpart. Smooth transition!

One thing that's bugging me is that users who don't want to create  seamless tiles will probably want a generic rectangle tile to which  they can apply any transformation they want, just to see which looks most interesting. But if you want to create a seamless tile, you have to define a specific guide from the start... Unless I just make guides and transformations to later apply independent.

If you then apply a different transformation, that won't end up with a seamless design, that's your problem?