How to prevent a line break with an H1, H2, H3 tag in a text block?

Hello,

I would like to use normal text (paragraph/body) style text in a text block and H6 style. But after H6 there’s a line break and I don’t want that.

<h6>1994 – 1996</h6>
Federatie Goud en Zilver, goudsmeden

I already tried to change this in the Quick Css with:
h6 {
display: inline;
}

and
h6 {
display: inline-block;
}

and with !important added, but nothing changes.

Is there a simple solution?