Well, a quick fix if you want the default GUI you can add in your constructor:
auto defaultGUI = magicState.createDefaultGUITree();
magicState.setGuiValueTree (defaultGUI);
That should also bring up all parameters as sliders. You can start reorder things there and play around.
If you saved your tree using the file menu, you can add that xml file to the binary data and call instead:
magicState.setGuiValueTree (BinaryData::magic_xml, BinaryData::magic_xmlSize);
FTR: this post is the most uptodate explanation how to use it:
I know I need to record an updated video as well, so poeple don’t look at the old ones.