Changed how ShelfButtons are identified for in-place updating. They now fallback on using the `key` attribute if `docTag` isn't set, the `key` is then serialized into `docTag` for future updates.
Changed how ShelfButtons are identified for in-place updating.
They now fallback on using the `key` attribute if `docTag` isn't set,
the `key` is then serialized into `docTag` for future updates.

theodox/mGui