Although saveeditonline.com and TwineHacker are viable options, you don't necessarily need to use either. There are options native to your browser when it comes to Twine games using Sugarcube (rather than Harlowe).
Please note I'm not an expert, but to access these native options:
1. While in your browser window for the game, hit F12. This will bring up the DevTools window pane.
2. Select Console from the tabs available (e.g. Elements, Console, Issues, etc.) Note that in some browsers this is at the top of the new window, whereas in others it will be at the bottom.
3. You will see a right carrot/arrow prompt. This is where you will input commands to edit variables.
4. To access those variables in Twine-Sugarcube games, this begins with: SugarCube.State.variables
e.g. > SugarCube.State.variables then hit the enter key to input
5. Once entered, you will then be able to click the solid arrow to expand the entirety of the variables for the game.
6. After being able to see the unique variables of the game, drilling down into them is a matter of modifying the input from step #4. e.g. SugarCube.State.variables.money
7. The example of 'money' above will provide you with the current state of that variable (e.g. 100) but if you want to modify it, all that you have to do is change your input to equal a new value.
e.g. SugarCube.State.variables.money=500
8. Note that different variables require different data types. For instance, money is a number and so can be input as such, but say you wanted to change the player name. That's what we call a string and requires designators. You'll know that a variable is a string if its initial, unmodified value is bound by quote marks '' (e.g. 'john doe'). To modify a string variable, you would instead input:
SugarCube.State.variables.playername="john smith"
9. The other type of variable you might encounter are boolean, which is to say that they expect a true or false value. Unless you see the existing value bound by quotes, then any edits to that value must be solely true or false.
e.g. SugarCube.State.variables.worked_today=false
note: technically there are boolean value variables you will see as 0 or 1 as well, so be aware those can be toggled similarly.
10. Lastly, please note that variables can be nested. For example, they could be in the format of:
SugarCube.State.variables.relationships.best_friend
Or they could be in an array:
SugarCube.State.variables.inventory[0].quantity
You'll need to play around with it some to figure all of this out, but it can be quite powerful when playing Twine-SugarCube games that are still in development and full of bugs, broken game mechanics, or poor tuning/balance.
ProTip: you can use your keyboard's up/down arrow keys to scroll through previously entered commands, and your Tab key to autocomplete while typing out new commands. This can be especially useful because if something isn't autocompleting, you've probably created a typo and the command input will not work.
NOTE: you can severely and easily break your save using this, so do save before you play around. In some Twine-Sugarcube games they've enabled the backwards and forwards arrows for normal play. These will also allow you to back out of erroneous changes you may not have meant to make.
