u/CharacterPayment5

This has been asked on this subreddit before, but the previous poster was attempting to tile in all directions, I only need to tile horizontally... The other guy also didn't get any solutions I can work with.

I'm making a hand-painted cloudmap for Kerbal Space Program and I need to see how it tiles horizontally while I'm working so I can make sure the edges connect perfectly. Some planets in the game will require global cloud cover and I can't match it up through trial and error. I can't use the "Tile Perfectly" option because I don't like how it removes control over the result, I need to do everything by hand.

I am willing to find a new program if necessary, but it'll need a smudge tool and it'll need to run natively on Linux.