Can't customize format toolbar

I recently upgraded to Scrivener 3 for Windows and was personalizing everything (put on dark mode, stablish ‘spanish’ as the language, etc), but when I try to customize the toolbars, in the menu where you can choose the icons that will go into the format toolbar only 2 options appear: the and the , and nothing else. It has the current/predetermined icons on the right side, but when i take them off (click on the left arrow) they disappear, it doesn’t appear on the options menu at the left side. I had no trouble with the main toolbar, that one has all the options at the right side and I could customize it, but for some reason I can’t do the same thing with the format toolbar, and I really need to do it, since the predetermined settings don’t have some of the icons I use a lot, like the subindex :cry: .
(Also, i’m spanish, so I apologize for all the grammar mistakes)