If I click on the edit tileset button, I can edit the tileset properties, but as soon as I click on a tile, it is replaced with the tile properties window, and I cannot get the tileset properties window anymore.
Am I doing anything wrong?
I think both tileset and tile properties windows should be displayed (or there should be a way to select which to display).
It can be accessed from the menu, similarly to accessing the Map properties. For Tileset properties there is a menu item Tileset -> Tileset Properties (when in the tileset editor).