Ugh... those games are made with powerpoint? I worked for years in a company who had their system .. on Access 97 (for those who don't know, access is part of MS office suite, which includes powerpoint. I dunno if it still exists), so I guess the language is the same. So thanks but no thanks, I wouldn't code a single line of code on that language again. I'm going to compare it to Twine, which is the tool I use for my VN + Free roam game.
Showing images is not so simple, let alone the formatting of each dialogue box, or the entire programming of the NPCs, inventory, battles, etc... hell, if I had to change, I would learn ren'py from zero instead of touching anything related to powerpoint.
Sorry but no, I'm not doing shit on powerpoint. NEVER. I'm fine using twine as the dev tool for my game. And my game is what you call a "word game" since is heavily text based.