Powerpoint – deleting images – the image with relationship ID rId23 was not found in file

I realise you're after an actual slider control to do this, but PowerPoint is really just a sequence of effectively images anyway with the left and right arrow keys allowing you to step forward and backward through them already. If the slider was a visual thing, you could also put an image of a slider under the image you're showing with the control moved to the right notch, if this was so you could see where in the sequence you were up to. Anyway, is that something that might suit your needs?

Otherwise, you have two choices. Firstly, you can use "action buttons" which show up under "Insert" "Shapes" (right at the bottom) - you can make them shortcuts to "next" and "previous" slides. Actually, you can make any shape a hyperlink, so you could "construct" a slider-type set of shapes that look like a slider and in some ways act a bit like it as well (though you'd need to click around on it - click and drag probably wouldn't work like a slider does.)

Second choice is you start playing with VBA and believe me, that can get really painful and steep really quickly. I've written a sequencer controller that takes presentations from a database, builds it into a mega presentation, displays it, and looks for special slides which embed live web pages and activates them when the slide displays. And that's .net office automation, which is a bit more powerful than VBA.

I've run into this myself for updating weather images from the Internet during a slideshow.

Since Powerpoint stores the image files within itself while the slideshow is running, it does not update the images.

This means you have to trigger it to update the links by using VBA code or use an add in like; Update links during slide show Add-in for PowerPoint 97 or later or LiveImage - update inserted linked image real-time in PowerPoint.

I don't use that program any more and can not find the code I once used. The above information should help you get where you want to be.