I have wanted the same thing, eg. for a bed tramming G-code that lets me measure for any length of time, but I have yet to find a solution. You can pause and hover for n seconds (like the official tramming G-code does) or you can pause until user resumes - but in the latter case it moves to the chute.
Given that the only user-intervention pause command we know is “M400 U1” and Bambu has yet to release any G-code documentation, I have to confess I’ve had the idea to try out things like “M400 U0” or “M400 U2” just to see what happens…