We also can't blindly delete unused gradients -- sometimes the user might want them preserved (e.g. because a downstream tool uses them,
or
because they are intended to be referenced from other SVG files).
True.
It's probably better to provide some means to mark gradients or other SVG objects as "garbage-collectable" (e.g. an inkscape:gc-policy attribute?) -- new gradients and such created by Inkscape would be marked as collectable at first, though the user could mark them as permanent if they so chose.
I don't quite get what kind of behaviour you're trying to describe. Anyway, why not just have a delte button left-side of the edit button for now? That way the user can easily deside to remove any gradient he or she wants to.
But talking about gradients and colors I'd love to see the whole ui being redone, though I'm not a hundred percent sure yet, what it would best look like. I'm thinking of something that is indesign like, with swatches and gradients to choose from.
Take care
David