Is there a way to ignore the multiclassing requirements restriction? My DM okayed it, I just want to make sure it's possible, otherwise I can't have my character on Dnd Beyond. 

Officially no. But you can try setting the appropriate ability score to the required amount, adding multiclass levels then readjusting the score back. If this causes an issue then set the score to what is needed and use a homebrew item or feat to set the score back. Multiclass levels do not get removed if an effect reduces your score.

Just wanted to say that at first glance, this seems to be working. Wanted to make Paladin available to one of my players. Their charisma was high enough, not strength; but dexterity was. It also fit into the story as well as the way I was developing the gods in my game.

Backstory done onto the step by step.

1. In your character sheet, click the stat you need to adjust (strength in my case). 

      1a. Enter the required number into the "Override Score" field; and click out of the pop up.

2. Select "Manage Levels" from the character drop down menu.

3. Select "+ Add Another Class" at the bottom of the screen.

      3a. Add the desired class.

4. Return to character sheet and undo the changes made in steps 1 &1a.

5. Revel in your (DM approved) new class.

This information was extremely useful for my DM and I! Thanks! :)

On the “home” tab of the character builder there is this: 

Use Prerequisites

Allow or restrict choices based on rule prerequisites for following this character. 

• Feats 
• Multiclass Requirements

Toggling that off should do it too I think.