Memento Yearbook currently allows you to design on a single album side. Should you need to design a double-spread with images & text across the gutter, position content off the edges of facing pages.
First design the left side of your page, positioning frames extended over the gutter. You won't be able to see the part that is hanging to the other side of the page. Once the frames are in position, select any content that needs to spill over to the right page, and copy it (Ctrl-C on Windows, Cmd-C on Mac).
Click Edit on the right side page, then paste the copied content to that page (Ctrl-V on Windows, Cmd-V on Mac). Position the frames so that they are aligned to the other side of the page.
In the following example, these two pages have a duplicate photo and text frame positioned off the gutter edge of adjacent pages.
For example, a double spread with an image right in the gutter might print to look like this, or worse. Notice the break in the line of the wall and the cut-off shoulder because the photo is stuck in the binding itself.