Previously, in Marble Blast Platinum, you'd need to copy an example mission manually in order to start creating. In PlatinumQuest, it's much simpler. While on the level select screen, hit the Menu button, and then select Editor. A window will pop up allowing you to not only edit existing custom missions, but also create new ones.
Hit "Create New" to bring this dialogue up, where you can configure basic aspects of your level -- such as name, description, author, gamemodes, etc. You can even import your QuArK or Constructor interior from this menu -- just type "<YOURINTERIORNAMEHERE>.dif" in the "Interior filename" field. Simply hit "Accept" to load your new level and begin using the level editor as normal.
To start off, the bottom bar is one of the most important new additions to the editor, as it contains useful features no matter what you intend to do. When you have nothing selected, you can change the level's current skybox ("Change Skybox"), or, perhaps, open an ultra-detailed menu that allows you to fine-tune and tweak every technical aspect of your level you could possibly want ("Edit Mission Info").
With most objects selected, you'll be shown four options: "Translate" and "Rotate" allow you to move an object to an exact point in space, relative to where it currently is or not, and "Drop to Ground" will lower the selected object until it is resting on an interior. Lastly, "Parenting Config" is an advanced option that will allow you to connect one object to another so when the parent moves, the parented object does too.
More options may be shown depending on the object selected; objects such as start pads, signs, and fading platforms will show a "Skin Selector" option where you can select the desired appearance from a list, and path nodes will show a "Edit Path Node" function which will allow you to tweak it to perfection.
A few more miscellaneous things you can use while editing:
Applying the Final Touches
Wow, you finished your level! How do you pretty it up for display on the new level select screen!?
First, you'll need a camera path. While in freecam mode (Alt+C or select from Camera menu at top) simply press M to drop a CameraPath node at the camera's current position and rotation. These nodes will automatically connect to each other, however, if you'd like the path to loop, you'll need to set the "Next Node Name" of the last node to "CameraPath1".
After your path is set up, adjust the "Time to Next" for each node to create a smooth, coherent path. If you want a cut to another "scene" of the campath, set its Time to Next to 00:00.001. Make sure your path isn't too jerky or fast, as it could throw off some players and it will generally be very unpleasant to watch.
To save an image to be used as a preview while it loads, all you have to do is select File -> Get Preview Picture while in the editor. This will take a 1280x720 image of your level from the position of the first CameraPath marker and save it in the same folder as your .mis file.
When you're ready to make your level's icon for the menu, press Ctrl+P to take a screenshot of the level, and then navigate to it in your PlatinumQuest/platinum/data/screenshots directory. Open it up in your favorite image editing software, and then crop a portion of it and resize it to 96x70 pixels. Save it in the same spot your .mis is saved with the same name, and you're good. In order to update the level icon and level preview, you need to restart PlatinumQuest.
That's pretty much it for the basic aspects and improvements of the editor in PlatinumQuest. If you have any further questions, feel free to leave a reply to this thread.
Follow me on twitter at @threefolder