Hi LuDK!
As in 2.7, to delete a tileset you have to first delete its material. Find the tileset material in the material panel and press the "X" button while holding shift, then save your blend file and reopen it:
Blender will delete the material and it should show up as "Invalid Data" in the tileset list. Sprytile will eventually delete it for you when you add new tilesets, but to delete it right away click on the down arrow icon and choose "Validate Grids":
Regarding the view not showing, it usually means you are working on an object which currently has a different tileset than the one selected.
Hope that helps! :)