In diff mode, deleted lines are indicated by a colored block (green below). The 'number' line numbers are skipped for this block.
Is it possible to emulate this behavior (screen-width colored blocks that act as separators) with Vim commands in a script, or is this only possible for diff mode from specific Vim internal C code written for this functionality, but not exposed through any Vimscript API?

diffexprto manually set where the blocks go. – Mass Jan 08 '21 at 21:56