The exact feature you need is part of the new version of Pix4Dcapture that was released last week for Android! Among other, you are able to duplicate missions using the Project List.
Android Pix4Dcapture (3.0.1), release notes: https://support.pix4d.com/hc/en-us/articles/210447423
How to use the Project List: https://support.pix4d.com/hc/en-us/articles/208820126
The overlap that can be selected in the settings is the frontal overlap which is also related to the side overlap. However, the side overlap is slightly smaller than the frontal one. Basically what the application does is that it finds the distance needed between 2 images to have the frontal overlap selected. To compute the distance interval between the lines and so the number of lines in the grid, the app uses twice the distance between the images that defines the frontal overlap.
The side overlap is a bit more flexible because it depends on the number of lines of the mission. For example for the same frontal overlap, if you have 2 lines and you stretch a bit more the size of the mission, you will get pass a threshold and the app will compute that a new line can be added and the mission will have 3 lines for the same frontal overlap. In that case the side overlap will indeed be different between 2 and 3 lines but the frontal overlap will remain fixed.
Hope this information is useful.