Trying to use /happytrails setHappyTrailSpeed 2, and it does not appear to do anything. See picture:

I'm in Creative mode and using HappyTrails-1.16.5-1.36.0.8

Woops never mind. Thought it would change the file I had on defaultconfigs, instead is changing file in save/serverconfig.

Thank you ! It's odd because I thought I had moved all of our configs /serverconfig to /config.
Glad you got it working but I need to fix this because I've found out that /serverconfig files are more difficult to work with when building modpacks.

Yep - they're a real pain when you're building modpacks.

Are you using 1.16? Planning on checking this and changing it within the week if it is still in serverconfig.

Yep. 1.16.5. Just building a private modpack.