There are a few shortcuts you can use within ManicTime.

On any view:

• Ctrl-Tab - cycle through the tabs

On day view:

• T - open Add tag dialog. If selection is already made, then the dialog will show up without time fields.
• D - If you select some already tagged time, D will delete only Tags and keep all other data inside a selection.
• Ctrl + F - Focus on Filter textbox at the bottom
• Ctrl + Shift + F - Open Search window
• Home or F9 - Today
• PgUp or F7 - Previous day
• PgDown or F8 - Next day
• F5 - Refresh (or go to Today)
• Ctrl+D - When autotags timelines is selected, it will toggle diagnostics mode

You can also configure Global shortcuts in Settings or Tag shortcuts in Tag editor.