but then at the end in the excel file I see always in the "Image [Image]" column some strange strings (*) and I don't understand where I am going to save the photos !! (although in truth I can see the photos inside the app!).
I was expecting at least to find in my OneDrive a subfolder with the images inside, but it isn't ..
These strings are actually the pictures you saved, they are file content in Base64 format.
Base64 is an encoding algorithm that converts any characters, binary data, and even images or sound files into a readable string, which can be saved or transported over the network without data loss. ... Base64 images are primarily used to embed image data within other formats like HTML, CSS, or JSON.
I've made a test but did not encountered the problem you mentioned:
1)create an excel file , insert a column named Image[image]
format data in excel as a table
upload this excel file to one drive
2)connect your app with the excel table in one drive
3)insert a Add picture control
4)Add a button control and set it's OnSelelct property: