I tried to enable it on my sandbox testing world and got an error, 'no character' on line 783 in control.lua. If it makes any difference, I used a console command to make everything unlimited before, save file is here if you want to test it: https://1drv.ms/u/s!Ai6sg-RxOdJhkFzA5BTLang0vfkD

Also, if I try run your mod alongside Test Mode on any map, I get an error saying a GUI element with name popup is already present in the parent element (line 687 of control.lua)

oooh, I have checked the character when increasing player's reach but forgot to do the same when increasing player's mining speed. My fault. Will fix it in the next version. For instance, you can turn off increase_player_mining_speed_when_enabled in config.lua and that line of code will not be executed, and also reset_player_mining_speed_when_disabled if you will need to disable Creative Mode.

For the second problem, I think I know how to fix it. First time to know the GUI element names are shared across mods. Sorry for your inconvenient.

Thanks, I just searched for increase_player_mining_speed_when_enabled in control.lua and copied the character check over to it, it seemed to work :)

Yes. It is the cause of error. I originally planned to upload the fix today but due to some additional problems, I have to delay it to tomorrow. Please bear with me. :)

Version 0.0.3 is released with the bugs fixed. Please feel free to try it and continue to report bugs if there is any. :)