Maybe someone else is having this problem?
How to create a macro on VIA?
A macro is a series of keys pressed together to perform an action, now, you can program to just use one key to perform the same action, for example, holding Shift+Command+4 (screenshot on macOS) can be done with just one key. Here is how:
1. Go to MACROS on the top left corner of the Configure tab.
2. Search the keycodes that represent the key you want at https://docs.qmk.fm/#/keycodes_basic, then, copy and paste the Aliases on the page onto the VIA.
3. For example, enter {KC_LSFT,KC_LGUI,KC_4} in the Macro 0 box area, and press Save. The M0 key will become Shift+Command+4 (screenshot on macOS).
4. Select the KEYMAP section, click on the key that you want to replace, and the key will then flash slowly on VIA. Go to the MACRO section on the lower-left corner, click the M0 key, and it’s done.
This info courtesy of Keychron's site
ETA: On a side note, it still doesn't perform the desired functions in reaper. The single key commands are fine but for some reason, the macros want to open a little data box for setting metronome tempo?
Maybe I can figure that out in the reaper discussion forum.
further ETA: Well, crap. I see now that the braces are necessary. {random macro}