The source code indicates that some special behaviour is intended when pressing the home key for slurs:

Happy to make this change if it's agreed what the new behaviour should be - I did a fair bit of work on this a few years back, so it's even possible something I introduced. Does 3.6 have the same problem?

3.6 works correctly. I would suggest just returning that behaviour (i.e. Home key always just scrolls to start).

We can then decide on a new, more logical, shortcut for the "reset current handle" functionality. I would propose the R key, in line with Ctrl+R for "Reset shapes and positions".

@bkunda Agree?

There is quite a lot of code to support the Home key as a special case, even this:

bool EngravingItem::isEditAllowed(EditData& ed) const
{
    return ed.key == Key_Home;
}

bool EngravingItem::edit(EditData& ed)
{
    if (ed.key == Key_Home) {
        setOffset(PointF());
        return true;
    }
    return false;
}

which seems odd...but it strikes me that this behaviour should only occur in edit mode (much as I'd like to get rid of edit mode, we're stuck with it for now...). And the code suggests it should only kick in when a particular grip is selected...

Ok I just retested and Home works fine when a slur is selected. Only behaves differently if you select a specific grip - but:
a) on my keyboard (Windows laptop), this is only true for the "Home" key above Num Lock, NOT the Home on the Num. Key pad!
b) it doesn't actually reset the grip position anyway! Code definitely executes but doesn't seem to do anything.

Maybe initially reported issue is Mac-specific? In which case I can't really help sorry...

I don't think it's Mac-specific. The behaviour I'm seeing is similar to what you describe:

• Whether scrolling works while a slur is selected seems to depend on how it was selected. When I click directly on the slur, the grip handles become visible; in that case, scrolling doesn't work. When I select the slur via Shift+drag, or by Ctrl+clicking it twice, or any way that doesn't cause the grip handles to become visible, scrolling works fine.
• I'm not sure about numeric keypad since I don't have one.
• Whether "Home" actually resets the handle position, seems to depend on which handle. The upper left and upper right handles do respond, but the others don't.

The "off" property for at least some of the handles doesn't seem to ever be used. I would think it would be quite useful to request a specific handle to be reset to its default position, but I'm not sure how feasible that is - it's not clear the information is even stored in a way that makes that possible. However I just observe something weird where it appeared to work providing I also used Home on another handle too.

Hmm, weird though, now I am able to reproduce the behaviour initially described even though no grip handle is shown as selected - and I can see how to fix that much at least.

Think I might have figured it out with the middle grip handle - you have to reset the offsets of the two either side.

So with my fix the new behaviour is:
Home key only resets a grip handle position IF you actually have a specific grip handle selected.
It now works for the "shoulder" grip handle, which is basically the apex of the slur. But not for the handle that is shown directly between the start/end handles, as that represents the overall slur offset. Can do that one do easily enough.

However...I also noticed that UNDO doesn't work properly when using Home key like this (it's not done via an undoable action).

Fixed Undo too. And Ties. However "home" still does nothing if the "drag" grip - which controls the overall relative position of the whole item on the score - is selected.

It is a Mu3 regression