How do I set a choosen text font for a slide show without having to adjust each text on each slide.
Do I have to create a snippet and how do I do that?
The easiest way to get started is to create a new slideshow. Then insert a Blank Slide. Then choose to Add Text. With the text block selected (it should be automatically when you added it), go to the Options panel, go to the Text submenu, then choose a font, style, alignment, size and color (other settings are not remembered). The next time you add any text it should take on those settings. So, no, you don’t have to create a snippet.
Thanks for your answer. I understand FM does not have a possibility to change the standard initial textsettings.
I also understand that you have to create a new set of settings for each new slideshow.
Too bad FM lacks that option or am I wrong?
No, you’re not “exactly” wrong 
The “initial text settings” that you mention are saved from the LAST TIME you used the application (it’s all saved in the .plist file, I think). So if you created a slideshow using font Helvetica (with all the parameters mentioned before), for example, and that’s the font that’s set in the Text submenu when you exited the application, then the next time you create a new slideshow, that font (and styles) carry over to be used again. It works like that for me.
Thanks for your bright explanation. In the meantime I created a snippet with which I also fix the fading in and out of the text in a particular slide.
Thanks for your time.