When you right click (Ctrl+click) a transaction, you'll see following menu -


Add Attachment -
Attach image files to a transaction. This is detailed further in this article.

Create Reminder from Transaction -
Create a Transaction reminder. LINK

Duplicate Transaction -
This will open the New Transaction window and fill in the current information that can be edited.

Show Other Side -
This will open the register of the other account/category involved in the transaction.

Mark as Uncleared -
Transaction becomes uncleared, and the green cleared symbol will be removed from the 'C' transaction field.

Mark as Reconciling -
Transaction is assigned as reconciling, and you'll see a diamond symbol added to the 'C' transaction field.

Mark as Cleared -
Transaction becomes cleared, and the green cleared symbol will be added to the 'C' transaction field.

Batch Change -
Make changes to a single transaction, or multiple selected transactions at one time. LINK

Delete -
Delete the transaction.

Single Line Mode -
Set the register to display only the Description line entries.

Two Line Mode -
Set the register to display both Description and Memo line entries.

Sort by -
Sort the register by a specified set of variables. Sorting the register is detailed further here.

Ascending -
Sort the register from earliest to most recent date.

Show Transaction Details -
Display all information associated with the transaction in the format it will be saved to the data file. Generally only used for technical support issues.