Synergy One-to-Many Keymapping

Question

Overview

I'm trying to map both Ctrl and Alt on Ubuntu to Cmd on MacOS.

Progress

So far, I have only been able to map Ctrl or Alt, but not both.

Attempted Strategies

In my .synergy.conf on the host (Ubuntu), I have tried the following:

1. Valid syntax, wrong results (only Ctrl), expected success:

   section: screens
     desktop:
     mac:
       ctrl = meta
       super = alt
       super = ctrl
   

2. Invalid syntax, reasonable strategy, expected success:

   section: screens
     desktop:
     mac:
       ctrl = meta
       super = ctrl, alt
   

3. Valid syntax, wrong results (only Ctrl), didn't expect success:

   section: screens
     desktop:
       alt = super
     mac:
       ctrl = meta
       super = ctrl
   

4. Invalid syntax, reasonable strategy, didn't expect success:

   section: screens
     desktop:
     mac:
       ctrl = meta
       super = (ctrl, alt)
   

Documentation

I have failed to find helpful existing answers on SO, U&L SE, or elsewhere. I also read the official Ubuntu documentation.