Hello @Mario Luque,
That has changed in a recent version of Apptio, I believe in 12.9.5. I will follow up with my education team to have that updated in our guides. can you tell me which course/guide you are working through?
If you want to edit manually, instead of creating a new 'table" you create a new "editable table". From there, you can enter data in the screen shown below.

Kind regards,
Debbie
#ApptioforAll