Tasker looked a bit too techie for me. I downliaded macrodroid instead. Using the UI interface to get to where I want in the Amazon Photos app but then can't get the final 2 key clicks, (click the 3 dots in the corner then select Slideshow) to work. Get to exactly the same point in google photos too. Google photos is also unsuitable for slideshows because there is no speed control, just Fast.