Despite the instructions, you can modify a Johnson 1500 SC to both soft close and open for a 24 inch door. The reason Johnson doesn’t do so is to maintain the same system for every door size (cheaper). The technical issues preventing it are
1. Maintain ability to replace track hardware by keeping it removable at finished end of door.
2. Maintain same set of instructions, measurements, cuts, and hardware for every door size.

I’ve modified my Johnson 1500 hardware to work with a 24 inch soft open and close.

For anyone wondering how, this is what I did.
1. When cutting the frame, do not cut the track shorter than the rough framing opening on the unfinished side of the door like the instructions say. Cut it flush with the wood at the width of the rough opening. DO NOT USE THE PREMEASURED CUT. IT WILL BE SLIGHTLY SHORT OF YOUR ROUGH OPENING.
2. Modify the unfinished side of the frame’s steel end cap. Remove the two tabs that support the aluminum track and grind the bumps from the support of them flush. You can either cut the aluminum track a tiny bit shorter to account for the angle support bends in the steel end cap, or you can grind small knicks into the track so they fit and finish flush. I went for the grind small nicks method.
3. Remove the aluminum track.
4. Inset the steel end cap 1/8 deep into the frame so that it’s flush with the wood. Your track should sit evenly on it – you don’t want it to bend when you screw it in.
5. Replace the aluminum track, drill a hole in it that matches the location of the screw groove from the steel end cap and affix the steel end cap with a screw to the wood frame and aluminum track. This provides the support we removed in step 2.
6. The finished side of the door’s steel end cap needs to be inset so that it’s flush with the wood crossbar as well (you’ll install track over it too)
7. Add a 2 3/4 inch piece of aluminum track to the end of the track on the finished side of the door. There should be plenty of scrap to make it. This makes the track go almost flush to the steel end cap, just like the unfinished side. You’ll want to also take the full track off the frame so you can true the end of it so it’s a smooth transition to your small piece. It is important that you keep this small track separate! It needs to be removable in the future so you can replace the hardware if needed. Affix it with at least 2 screws. You’ll need to drill holes, but similar to the other side you can use a screw on both the end cap and the track.
8. Install your door hanging hardware on your door, but instead of 2 3/4 from the edge go flush with the edge. This allows you room for both of the soft close assemblies and critically margin to true the door with the frame.
9. Assemble and install the frame following the instructions as given by Johnson.
10. After hanging the door adjust the position of the stops on both the open and close side to provide 3/4in for the door jam.

That’s it! It’ll take a few hours but in my opinion it’s well worth the effort to have soft open and close in both directions. I know it was going to drive me nuts that my 24 inch door only had soft close in one direction while my 30 inch ones were in both.

Did you need to install any sort of plate on the side where the sliding door touches the inside of the frame (like… when you head to the toilet room and close the door behind you does that pull edge thingie just hit the inside of the frame or is there a plate for it to hit?

Really nice design all around. My husband and I are hoping to use pocket doors in our room and bathroom. I really like the frosted glass and wood door. What brand is it? Or where did you get it?
Thanks