QGIS - delete column from Attribute table. I use SpatiaLite Layers

I want to delete a column from Attribute table but the function "Delete columns" isn't highlighted. (When I am adding new layers I use New SpatiaLite layer, not Shapefile layer). So I have installed the plugin Table Manager but when I delete a column using this Table Manager the function "Save" isn't highlighted. Only "Save as" is possible. Is there any advise how I could delete a column? Thanks.