POSTERINO 3 - EASILY FORGOTTEN IMPORT FOLDER

I run an active alumni group for my high school.  Every now and then I would make a photo-grid of one particular teacher.  The grid shows photos of the teacher, in chronological order.  It's nice to see someone changed over the years but certain features would stay the same.  I use Posterino 3 on the Mac to make the grid.  The software is great for that kind of thing.  Ideally, this is how it works:

1. Set up a grid.  In the example below, it's a 4x4 grid.
2. Select the folder to import images from.
3. The photos from that folder show in the little gallery to the left of the grid.
4. Either drag individual photos into the grid, or fill the grid up alphabetically, or even randomly.

I love the idea of a template and Posterino has the feature, but documents created from my custom template wouldn't show the images available.  The only way to get the images to show, at least to me, is to carry out these steps:

1. Create new document based on the template.  The grid is there, with the editable years that need to be adjusted depending on what years' photos I have for the teacher.  The years also depend on how long the teacher stayed at my school.  Unfortunately, there are no photos to the left of the grid.  The screenshot shows some images I placed in the source folder.  They should be part of the template file, at least I think they should be, but they are not.
2. Select the source folder by selecting File/Import Images as in the picture.  I would love to avoid this step but it's the crux of the problem.  Even after I selected the source folder, nothing would show up.  Very weird, but that's why we are having this conversation.
3. Create a new document, again!  Use any existing template.  I stick to the standard ones instead of the custom one I made, just to be clear which one is which.
4. Immediately close the new, second document, without saving.
5. Boom!  Somehow the action of creating a new document forced Posterino to load the images in the source folder.  Maybe it's because I'm still using an old Mac, maybe it's a bug that is to be resolved later on.  I am fine with my workaround for now.

Before I came up with this "solution", I worked off folders named for the teacher.  Now, everything has to be in a folder called photo-grid.  As I am done with the project I would copy the folder's content to another folder named for the teacher.  It may work if I change the source folder every time but I think it's easier to see where things are with the five steps above.