Adjust UI elements (size/scale) on HDMI display

I have Volumio up and running on my Rpi 3b, and have connected a 5.5" touchscreen over HDMI. My particular touchscreen seems to have trouble (refuses to) display other resolutions besides 1920 x 1080. This results in the UI elements being impossibly small. I have tried every permutation of HDMI_CVT and HDMI_TIMINGS that I could reasonably come up with.

How can I get Volumio to draw the UI elements at a different resolution on the HDMI display?
Can I change the scale of the UI?
Can I rearrange and rescale certain UI elements?

Using grid view rather than list view helps a bit, but that is only a small portion of the overall interface. Many thanks!