Feature request: Display / custom per screen Fractional Scaling

[mfroment]

 * Cinnamon version 4.6.7
 * Distribution - Mint 20
 * Hardware: GTX 1080 / Driver: nVidia 450.57
 * 64 bit
 * (no error)

Issue
Fractional scaling is available in Cinnamon 4.6.7, but only in specific 25% increments.
For multi-monitor setups where PPIs do not match and are not in one of the available ratios, it would be convenient to be able to set the values manually.
For instance, I have 1 monitor with PPI = 109 and 1 monitor with PPI = 94. In order to have windows moved from one screen to the other keep their physical dimensions, assuming 100% scaling on first monitor, I would like to set the scaling on the second one at 86.2%.

Other information
At the moment this is not possible via the GUI. It can be worked around by manual editing of .config/cinnamon-monitors.xml (see attached).

Configuration info, if applicable
N/A

cinnamon-monitors.xml.txt