Would like to know how to change the picture saving path, for import of picture for items etc.
Picture is saved in a system table. To change this you would have to modify the function that saves it there. Even then I think you would need to effectively duplicate it as the item table holds a mediaid reference which is a system table. Check out page 346 for more detail.
This blog might be of use if you need item images to live somewhere else but pay reference to them from within NAV: d365bcangle.wordpress.com/.../
An on premise connector will be needed to use the power platform.