I'm afraid that's not possible It used to be possible a few patches ago, but I think the developers disabled the ability to change the patch number of a build. The reason for that is that people would carry their highest upvoted build and keep editing it to accumulate more and more upvotes but maintaining the highest-ranked build. Basically if one were to able to change the version number to PTR, anyone with 200+ upvotes on the build could just switch it to "ptr version" and it would be the #1 build in the next patch again.
I've just created two builds. The first one showed up without any issues but the second one almost immediately disappeared. Then, while editing the first build, it disappeared as well. Would love to figure out why they went away!