There should be an option to select multiple accounts, choose that option first & then select your accounts.
Resolution for '1099 mapping issue: 'How do I enter more than one account in box 7 during 1099 mapping?' available: Yes.
The 1099 mapping issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the 1099 mapping issue yourself by looking for a resolution described in the article. If it is a complex 1099 mapping issue or you are unable to solve the issue, you may contact us by clicking here or by using other 1099 mapping support options.
For more information about resolving issues related to 1099 mapping in Quickbooks/QBO or to get support for the issue 'How do I enter more than one account in box 7 during 1099 mapping?', click the link below: