You can now add the Manual Entry page in Salesforce Classic and track time for Projects/

To add the Manual Entry page

Log in to Salesforce as Administrator

Go to Projects view page and click the setting tab and click on Edit Object

Click on Page Layouts

Select the page to which you want to add the Manual Entry component

Scroll down to see "Visualforce Pages" and click it,

Drag and drop the "Section"to the Page layour at the boot

Now enter a name to the new section (Manual Entry)

Select the Layout and click the OK button.

Now the section is added to the page layout

Click the Spanner icon to add fields to the Manual Entry section

Save the page.

Now the users can add time on the Projects they worked on using the Manual Entry page in Salesforce Classic.