QB Issue Resolution:

 No, sorry. There’s no way to do that. But you could click the gear in Feedback and request that feature. That would be a good one.

Resolution for Issue 'Is there a way to link an attachment (after you have bulk uploaded them) to an existing expense/check bank transaction? I can only see the option to create a new expense.' available: Yes (Solved).
Source: Intuit Community forum.

Is there a way to link an attachment (after you have bulk uploaded them) to an existing expense/check bank transaction? I can only see the option to create a new expense.: this 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 issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

Support for bank transaction
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Error Recovery for bank transaction [Canada]
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