Talking about front end gallery
currently if I create a new page and choose the option gallery ( choice page-gallery) it will create a new page to which I can add as many pictures as I want from all subfolders I may have.
however all these pictures are then placed into 1 page. I do not have the option to create multiple mini galleries ( as in folders) in that one page the same way I can when I use the system gallery .
Case: I create a page called projects and I want to have 3 "folders" one for each project and add multiple pictures to each. When visitor looks at page projects they have 3 choices of "folders" - mini gallery to choose from on the main page.
Using the default gallery: OK using the option Gallery when creating a new page: Not ok.
you are asking for multiple special_galleries.php files/pages? This is the page that organizes your 'gallery' pages. We have a 'galleries' page (singular) and 'gallery' pages (as many as you want to create). The later is the one you put your images into while the former organizes the 'gallery' pages you create as folders with an image as a placeholder.
From what little I looked at it would require a core hack, if even possible at all but what you want is easy to do.
Since the 'galleries' page only organizes your 'gallery' pages' folders why not just make a page with an image to represent each gallery and link to the gallery page directly? In essence it's the same thing. The 'galleries' page does nothing more than organize your 'gallery' pages by putting the first image as the folder icon and linking it to that 'gallery's' page. And you would just keep the galleries page hidden in the file manager.
You can do exactly what you want; however, you are trying to make the system do something it isn't designed to do. The 'galleries' in gpEasy is designed for someone to easily create a "one stop" 'galleries page' that links to all other 'gallery pages'--by default the 'galleries page' is hidden, I believe, thus I don't think it was intended as anything other than an organizer of sorts. What you want is to create a page (not a gallery) and design it to represent your 3 folders so that visitors can choose only one of those three and not see all 'gallery pages' within the 'galleries page.'