Okay so there is a setting under “Cursor Settings” → “Features” → “Partial accepts” which makes it possible to accept word by word with ⌘ + → (using macOS) but this is quite annoying when you just want to accept like one or two lines.
I think adding the possibility to use ⌘ + ↓ to accept line by line would make perfect sense here. Imo line by line is just the right level of granularity for stepping through the suggestions and accepting them. I’d be happy to hear more opinions on this.