TrySHIFT + BACK-ARROW (to select suggestion); thenCOMMAND-SHIFT-I (on a Mac; or however one converts to InputForm on your system: see menu Cell > Convert To > InputForm for the keyboard equivalent, maybe).
That does take care of it (and converts it into input form which lengthens the code however). Even if you don’t click on the ✓, the interpretation that you see in the box is accepted which is nice. There doesn’t seem to be a way yet to show the quantity without the box unless you switch to mouse.
As of Wolfram 14.1 on Windows, the ✓ button in the natural-language Quantity input box is currently mouse-only, and there isn’t a built-in keyboard shortcut to accept the interpretation directly.
A practical workaround is to press Ctrl+Enter again after the interpretation is displayed, which sometimes automatically inserts the quantity into your notebook. Another option is to use the arrow keys to navigate and Enter to confirm if the focus is on the interpretation, though this may depend on your specific front-end settings.
It’s a useful feature request, so you might consider submitting feedback via Help > Feedback in Mathematica to suggest a dedicated keyboard shortcut for accepting natural-language interpretations.
This should help speed up workflow if you frequently use Quantity input.
Hope it helps you brother.