Nearly finished UVHM in duo, but still in TVHM solo, how can i skip?

If you're any less than level 50, the easiest thing to do is probably to just play through TVHM's main storyline. Ignore every side quest. You'll be so overleveled for the content that you should blow through, especially if you have weapons at your level. Plus, as soon as you get to UVHM, everything will be level 50 minimum, and if you're not at 50 yourself yet, you'll be in instant trouble - every enemy will soak tons of bullets and feel like its own mini-quest to kill.

If you're at 50, and don't have weapons at or very close to that level, find some before you tackle UVHM. Anything at even 49 or less will start to have trouble. (The higher the rarity, the longer it'll last, and some weapons will survive especially long, such as a DPUH.) Buy greens from a vending machine if you must.

If you're 50 and have leveled weapons, then a save editor might work, but I'm not sure. I found an editor on NexusMods. I can't tell from the screenshots whether there's any info there on which game mode you've unlocked, but if it's anywhere, it seems to be in that editor's Raw tab. Hope you're comfortable with Regedit.