Code change:
import * as nls from 'vs/nls'; import { ContextKeyExpr, IContextKeyService, RawContextKey } from 'vs/platform/contextkey/common/contextkey'; import { IInstantiationService } from 'vs/platform/instantiation/common/instantiation'; <ins> import { KeybindingsRegistry } from 'vs/platform/keybinding/common/keybindingsRegistry'; </ins> export class GhostTextController extends Disposable { public static readonly inlineSuggestionVisible = new RawContextKey<boolean>('inlineSuggestionVisible', false, nls.localize('inlineSuggestionVisible', "Whether an inline suggestion is visible")); public static readonly inlineSuggestionHasIndentation = new RawContextKey<boolean>('inlineSuggestionHasIndentation', false, nls.localize('inlineSuggestionHasIndentation', "Whether the inline suggestion starts with whitespace")); public static readonly inlineSuggestionHasIndentationLessThanTabSize = new RawContextKey<boolean>('inlineSuggestionHasIndentationLessThanTabSize', true, nls.localize('inlineSuggestionHasIndentationLessThanTabSize', "Whether the inline suggestion starts with whitespace that is less than what would be inserted by tab")); <ins> /** * Enables to use Ctrl+Left to undo fully (partially) accepted inline completions (the completion is no longer visible then). */ public static readonly inlineSuggestionJustCommitted = new RawContextKey<boolean>('inlineSuggestionJustCommitted', false, nls.localize('inlineSuggestionJustCommitted', "Whether an inline suggestion just got committed")); </ins> static ID = 'editor.contrib.ghostTextController';

Related discussion:
text: <!-- Do Not Delete This! featurerequesttemplate --<!-- Please read our Rules of Conduct: --<!-- Please search existing issues to avoid creating duplicates. --<!-- Describe the feature you'd like. --When using Copilot, users would like to be able to only partially accept suggestion instead of the whole suggestion at once. The users demand either word by word or line by line completion. Desired behaviour: Press a predefined key and accept the whole suggestion. Use a predefined combination of 2 keys to accept the top line of the suggestion. (eg: For a suggestion of 3 lines, the user would need to press the combination 3 times to accept the whole suggestion). The prompt would not show the line already accepted.
this sounds to me like a UX problem. Is there a mock sketch for a potential solution here? Is there some other editor which already supports this? We can also discuss it in one of our UX weekly meetings.
I don’t have a mock sketch. No other editors are supporting this yet but it is a requested features. I wanted to get the discussion going (doing the same for the other editors) to understand the constraints around it as well.
Technically, I think this would be rather easy to implement. I'd love to hear some more UX discussion before we implement this thought. What key-binding do you have in mind?
do you have some UX designers on your team that would like to help here? Once we have some good ux proposal we can bring it in our UX weekly sync on Wednesday to start the discussion.
No I dont have a UX designer in my team. I ll see how i can come up with a suggestion and get back to you
This is similar to Solution for me was 'CMD + -' to accept a word at a time. Something similar here would be great.
Fish shell allows word-by-word completion using the <kbdAlt</kbd+ <kbd&;</kbdkey-combo, which—at least on macOS—is used system-wide for navigating text word-by-word. I notice that I keep trying to automatically use this key-combo, so big +1 from me. ( Did not realise this is the vscode repo.) 
awesome idea. since you said this is low hanging maybe we assign to July for the initial investigation? What do you think?
This would be great.