Hello again!
I am happy to share my second tip with the community!
I discovered by myself how to solve this question.
All we need to do is go to this directory:
/home/the-user-directory/Documents/Publii/sites/name-of-the-site/input/themes/mercury/
With a text editor, open this file:
index.hbs
Find the following piece of code:
<button class="filter__item is-active" data-filter="*">{{{things-among-here}}}</button>
Then, type the desired text inside the <button></button> :
<button class="filter__item is-active" data-filter="*">Tudo</button>
That’s it!