global trill line setting

Is there a global setting to disable trill lines, so that every trill does not have a line?

Yes there is. In Engraving Options (Cmd/Ctrl + Shift + E) select the Ornaments section and choose not to show the extension line.
That is then your default for that project.

There is a ‘Save as Default’ button at the bottom if you want to save that for all projects on that computer.

Thanks for the tip John, but in the Engraving Options>Ornaments section, I cannot find the ‘choose not to show the extension line’ section anywhere. Could you show a screenshot please? Thank you.

Sorry, just found it. This board won’t let me upload a screenshot, so it’s at:

Engrave Options>Ornaments>(Trills)>Extension line for trills>Always show