I am creating the button positions for a remote control that will interact with a full image of the remote. Although svg layers would seem a useful way of creating a fully interactive single file, I am using this in a system that will not support svg. So I need to create individual objects for each button and, using inkscape, I can get the object position which will help me overlay correctly in the target system.

So, as I have now got an image of the remote buttons, all separated by a transparent background, can inkscape split these into individual objects in the same position?

I think 'object' is the key phrase here:

What does the target system expect as an object ?

I remember doing something similar in the early 2000, for dvd menus.

If you are talking about making a purely bitmap overlay either as 'Swiss Cheese' or 'Islands' that can be done.

If you are looking to produce some kind of custom data format ( presumably vectors ) which is not svg, it depends.

yes it would be most likely the bitmap overlay Island option although the Swiss Cheese may work. I would not know until I tried that. I don't need special vector formats

It's hard to say without know exactly what your target is:

If you already have objects on a transparent background - is that not the objective ? 

In Inkscape you would typically, resize the canvas to match the image - Edit>Resize Page to Selection

Draw vector shapes which match the buttons then - Obect>Clip>Set

Then export png to an appropriate resolution.

I was doing this a while ago so wrote an Inkscape 1.1+ extension to save me a lot of time https://inkscape.org/~inklinea/%E2%98%85clip-out

However I may have misunderstood what you want to do - the extension automatically creates transparent png files - with either Islands or Swiss cheese or individual pngs for each objects ?