Greetings, @lucjan.
Let me guide you in viewing the expense transactions associated to your Projects.
Currently, the ability to add the Customer or Project column in the Expense page is not available. However, you can generate and filter the Transaction Detail by Account report. This way, you'd see the data your business needs. Here's how:
- Go to the Reports menu.
- Scroll down to the For my accountant section.
- Click the Customise section.
- Set the Report date.
- From the Rows/Columns section, choose Supplier from the Group by drop-down.

- Mark the following tick boxes.

- Click the Run Report button.

Now, you'd see a list of your expense transactions associated to a specific project. You can save the customisation you've made for future use. You can read through these articles to help you generate and manage reports in QuickBooks:
Visit us here again if you have other questions or concerns. I'm always here to help.