Cheat Menu.
JS Save Editor.
To avoid bugs, you're probably best off replaying the game, but using the above to set your level/appearance/equipment to what they were. It should be a lot faster the 2nd time, especially if you're max level.
The JS Save Editor can't add Perks, If you want to add some, you'll need to either edit your save directly, or use the Console.
JSONs can be loaded in Notepad, but I recommend a JSON reader, because the save is not formatted to be convenient for a human to read.
The Console can be opened with F12 or Control + Shift + J. The format for Perks is;
pc.createPerk("Perk Name", Value1, Value2, Value3, Value4, "Perk Description");
Values 1 - 4 are usually 0, but not always. The description never has a mechanical effect, so it can be whatever you want.