Any way to single step through gcode

linuxcnc does have provisions for single step, but it is not part of the QtPlasmaC gui.

What is the use case? For other guis that control a Mill (for example) single step "makes sense" because the tool spinning while the work piece is stationary generally has no repercussion. With an active plasma arc, sitting stationary would cause the material to melt until the arc was lost.

If you are wanting to check the program, and didnt want to just "dry run" it, one option would be to start the dry run, and then pause the works after it started X/Y motion. This would allow you to use the FWD/REV buttons in the cut recovery window to move through the program at your own pace.

No worries. I suppose one thing that's different from a mill to plasma is a mill cant "dry run". So you might find that dry running in conjunction with the cut recovery FWD/REV to be sufficient.

Single step on plasma machines is of not much use, example, step one go to start point, step two find material, step three fire the torch ... makes a big hole on material and extingushes the arc, so can not continue any more from the same spot.
PlasmaC and QtPlasmaC have "disable torch" that works perfectly as it does everything including probing without firing the torch, so you can test the entire gcode without making any cut.
This i use a lot, even for finding material 0,0 on machines with no laser cross.