Is there a work around for the limit (10) of soft credits that can be added to a contribution?
There is technically no limit in the soft credit : it's only a limitation in the public form.

If it's a rare case i would propose to simply add the missing soft credit using the API explorer :


go to menu Support -> Developer -> API Explorer v3 (or v4 but my screenshot is in v3)
choose entity ContributionSoft, Action create and set value for Contribution, Soft Credit Amount and Contact ID
Then use Execute button 


Like so :



Otherwise, you will have to create an extension to somehow overwrite the CRM_Contribute_Form_Contribution::$_softCreditItemCount value and it should do the trick :



  /**
   * @var int
   *
   * Max row count for soft credits. The value here is +1 the actual number of
   * rows displayed.
   */
  public $_softCreditItemCount = 11;