You can add a new time entry to your timesheet without using the main timer.

Go to your Time tab and find the heading for the day you want to add a new time entry to.

Hovering over the heading for that day will make the 'New+' button appear. Click this to create a blank time entry under that date.

You can click into the time entry to edit it - add time, assign contact/project/task labels, and take any notes for the time entry. When done, click the tick on the right-hand side to save your changes.