The mod select button no longer works due Forge not having the ability to toggle mods using a .cfg file. The only way to remove mods is to either delete them from the mods folder or (in the case of larger mods) remove them from the modpack.jar. Some of the mods in the pack need to be applied directly to the modpack.jar, which means that, to turn them off, you need to remove the files manually. The files can be found in .techniclauncher\MODPACKNAME\bin\modpack.jar. You will need to look up the mod you want to disable and remove the files that that mod modifies.