QB Issue Resolution:

Lower right hand corner of the footer
Save or Save and Close or Save and New

Even if you open a saved entry the same buttons will be there in case you make a change.

Do you have any type of icon banner at the bottom of your screen that is preventing you from seeing the full screen – or do you need to adjust your screen resolution to show t complete anhe entire page?

Resolution for Issue 'Forgot how to complete an expense entry. Once it’s in, I do not see an enter or submit button.' available: Yes (Solved).
Source: Intuit Community forum.

Forgot how to complete an expense entry. Once it’s in, I do not see an enter or submit button.: 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.

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