How to insert tab character when expandtab option is on in Vim

Question

When I\'m in insert mode and I have the expandtab option switched on, pressing Tab ↹ results in inserting the configured number of spaces.

But occasionally I

Answer 1

You can use in "insert mode". In insert mode, inserts a literal copy of your next character.

If you need to do this often, @Dee`Kej suggested (in the comments) setting Shift+Tab to insert a real tab with this mapping:

:inoremap  

Also, as noted by @feedbackloop, on Windows you may need to press rather than .