In current NeoLemmix, talismans are stored in the level, not the pack data. They can also exist in standalone levels now. As such, the level editor, not the pack editor, should edit them.
An additional problem that arises from this is that the pack editor modifies the folder structure, and creates levels.nxmi files where they may not be wanted. Probably not a huge deal on a finished pack, but can be annoying on works in progress.
("Both can edit them" would also be acceptable.)