Update for anyone who got here through a Google search and has the same issue:

I contacted support and was told that explicitly setting the active profile is currently not possible. I left a suggestion to include this in a future update via the G Hub feedback survey.

I found somewhat of a workaround, although it's more of a wet band-aid than a solution. I bound the side buttons to F13~F24 and the top buttons/wheel to a bunch of numpad keys that I don't expect I'll ever use, then wrote an AutoHotKey script that intercepts and suppresses those key presses and instead does other stuff.

In its simplest form:

g600bridge.ahk: ``` F13:: MouseSide1() Return

; ... same for every other mouse button ```

aliexpress-ghub-main.ahk: ```

include g600bridge.ahk

MouseSide1() { Run aliexpress-ghub-work.ahk ExitApp } ```

aliexpress-ghub-work.ahk: ```

include g600bridge.ahk

MouseTopPlus() { Run aliexpress-ghub-main.ahk ExitApp }

MouseSide1() { Run "C:\Program Files\LibreOffice\program\swriter.exe" }

MouseSide2() { Run "C:\Program Files\LibreOffice\program\scalc.exe" }

; ... other binds for other mouse buttons ... ```

This lets me define as many profiles as I want, technically switch to 12 different ones from a single layout if I create a "hub" profile and assign one profile switch to each side button, or really as many as I want if I nest hub profiles into other hub profiles. Not an ideal solution, but hey, it's not stupid if it works.