Like for instance courier new, times new roman, without scrolling the entire list?
The fonts that were last selected and used are automatically displayed at the top.
Use styles. You won’t need any more the font menu.
Thanks, but unfortunately they disappear after a while, I cannot understand the rule. For instance I am using a style defined with Times new roman and I want to insert a word in courier new. I need to scroll the long list to find courier new. Is there a trick to keep from the start courier new on the top?
I am using styles, but … i do not know how to pretend the style to admit random selected words with another font.
To be precise for instance Times … and Courier. MS word does this.
Put the cursor in the fonts list on the toolbar, delete all text in it, then start typing the font name. Start with Times and LO will auto complete it to Times New roman. Start With Courier and it will autocomplete to Courier new. What’s the problem?
the style to admit random selected words with another font
Contrary to Word, Writer has several levels of styles. Paragraph styles define the overall characteristics of the paragraph. Character styles can be applied to selected words to override the paragraph style attributes.
Read the Writer Guide to discover the variety and power of LO styles.
Just to add for friends of direct formatting 
The list of recently used fonts is in your user profile in file .../user/config/fontnameboxmruentries - you could create a “preferred fonts” template file and copy that fontnameboxmruentries.template by means of your operating at login time to the desired place (before you start LibreOffice - so take care to not have a “Start LibreOffice with system”-setting).
Thanks for exhaustive and clear answers. I am just learning Libre Office secrets… Inserted font names seem to be kept… I will also try other suggestions. Character style looks very effective.