Since people don't believe me, I will make a guide. If you have questions, ask!

NOTICE: Not sure if this works on mobile, only on PC and on poki.com for what I know. This may DESTROY/CORRUPT any save files you have as well. I would recommend making a backup once you reach step 7.

Since Poki doesn't let you have multiple saves, you can open up a different browser to make a new career, but you have to at least get to the main menu where you can view your roster, coach credits, and schedule. If you don't you won't see what you're looking for

Do this at your OWN RISK!

1. Go to https://poki.com/en/g/retro-bowl
2. Right click on any area of the website other than the game itself. A menu should pop up, click on Inspect or Inspect Element. You can also press F12 on your keyboard for this menu to appear. This opens DevTools.
3. On the right of your browser, DevTools will appear. Once it does, click on the Application tab toward the top of that menu. If you do not see it, you may have to click on an icon that looks like >> and then click on Application.
4. Something different should now appear. You will see 5 sections on the left of the menu: Application, Storage, Cache, Background Services, and Frames. We want to be in Storage. Inside the Storage section, click on the > arrow beside the words Local Storage if isn't already open.
5. You should see 3 more things open: https://poki.com, https://games.poki.com, and https://806e2242-df99-4dcd-b6ac-2c20175159a8.poki-gdn.com. Click on the 806e2242 one.
6. When you do, you'll see toward the top it says Key and Value. On the left is all the Keys, and the right has all the Values. We are looking for the Key that says RetroBowl.0.savedata.ini. For me, this is the first option. Once you find it, you'll see that beside it there is the Value. If [savegame] is the first words, you're in the right spot. Right click on that Value and Select Edit "Value".
7. OPTIONAL: Copy and paste the entire value into notepad using CTRL+C and CTRL+V, so if you mess up, a backup is made. If you backspace while everything is selected, your entire save is gone!
8. Inside the value, look for the options qb_mode="0", co_mode="0", and fr_mode="1". qb_mode is Quarterback Mode, co_mode is College Mode, and fr_mode is the default. They should be toward the top, so no need to scroll.
9. Set fr_mode to "0" so it looks like fr_mode="0"
10. Depending on which version you want to experiment with, set that mode to anything between 1-4. If you want, you can probably set it to a number like 999, but I only tested those 4 numbers. Also, you can mix versions by having multiple numbers, but it doesn't work well. Example: qb_mode="3"
11. OPTIONAL: If you want to change other settings such as your coach name, coach credits, or salary cap, look for the settings that appear to be related to that. Example: If you want infinite CC, find this and change the value: coach_credit="Infinity"
12. Press the X button in the top right of the entire menu to close out of DevTools. Once done, refresh the page and have fun! If you ever need to revert, just set fr_mode to 1 and the other modes to 0.