It should not be an option to select "Delete" when delete feature is not supported. If user by mistake has created a bunch of sliced sprites without noticing it, it is not possible to delete them from Assets folder (note, you need to delete the asset itself).

Prerequisite:
You need a sprite in you assets

Repro:
1. Select the Sprite from the asset
2. In the Inspector, select Sprite mode > multiple
3. Select Sprite Editor
4. In the sprite edito create, by slicing, a boundle of new "sub" assets
5. Navigate to the asset folder and select the bundle of "sub" assets" and right click
5. select Delete

Result: Nothing happens

Expected result If it is not possible to delete the "sub"assets, then Delete should not be an option

Note: By selecting the asset it self (the top level), it can be delete