Creating one image from two and storing it - App Designer

Hi,

I have created a application for DNA/mRNA sequence comparison and filtration. I have an option which allows user to save generated matrix as a image file with imsave.

Every displayed matrix is saved as an app.property and when user decides to, he/she can save this image but only the last generated one.

This is a dot matrix you get by clicking draw:

And after filtration:

So as you can see user can only save those two plots one by one and as separate files. I want to give user a option to save two images in one. What I want to achieve is an image composed of both of this matrices next to each other horizontally or vertically. I tried to store them somehow with subplots, looked for answers here on forum or tried it my self but that didn't work. And I also dont want it to be seen by user (the image concatenation, if that's correct name for it has to happen in a background).

I tried storing one image in one app.property after 'DrawButton' is clicked and then after 'FilterButton' is clicked in another but I have no clue how to get them into one picture.

I'd love your help and thank you in advance. If something is not clear, please let me know - I'll try to explain it more precisely.

Stanisław