Creating new powerups?

This is probably a pretty dumb question, but I didn't find anything relevant using the FAQ or search, so:

Is it possible to create new powerups (like the double jump, etc.)?  I had the idea of turning the player's ability to jump into an item, but I have no idea if the editor supports this.  I'm guessing the answer is probably "no," but I thought I'd check anyway.

On an unrelated note, where is the sign tile used in the KS tutorial?  I'm still pretty new to this editor and I haven't found it yet. >_<

You can't create your own powerups, but can simulate that a existing powerup its another kind of item, but it may require knowledge of shifts and flags.

And you can find the signpost tile in the tileset 1 (Tutorial tileset)

The sign object is mentioned briefly at the top of page 12 in the .pdf manual by SiamJam. For more detailed explanations on objects check out the object compendium.

To make your own image for a power-up:

• First, make a copy of the screen where you get the power-up.
• Second, include the image for the power-up on the original screen only.
• Third, put a shift object on the power-up image.
• Fouth, set the shift object to "Shift on Touch", point it to the copy screen, and set "Flag On" to the proper power-up.
• Fifth, on the screen with the image set "Flag A" to the same power-up and point it at the copy screen. This prevents you from finding the power-up after it's been collected.
• Sixth, put the warp object on the copy screen. (orange box with arrows)
• Seventh, set the warp controls for the copy screen so that when you leave you enter the same screens you would have entered if you left the original screen without collecting the power-up.

There are items in the system file that prevent the player from jumping; they're the tiles that say 'no jump' for some reason, and if you place them over a tile it will stop the player jumping when in this tile. Then you can use a power-up image you've made and use flags or shifts to make the character shift from a screen or set of screens with the 'no jump' tiles on every square the player can walk in, into identical screens without.

This level uses the technique near the start (this level is also seriously weird) (but it has wonderful music). Obviously the later into the level you put your jump powerup, the more work it would require.