I find Dorico puts too wide a gap between the tr of a trill and the extension line, but attempts to reduce it seem to have revealed some kind of bug. The default value is 1/8 space, which is clearly less than the gap which is in fact drawn—that looks more like 1 space. Changing the value to 1/16 or 1/32 space in Engraving Options has no effect at all on the width of the gap. Only a value of 0 brings the line up close to the tr as I want it—I could afford a tiny fraction more space, but this will do.
You might instead prefer changing the engraving option to place the gap at the end of the trill line rather than the start, i.e. set ‘Position of remainder gap for trill extension line’ to ‘At end of trill’.
Thanks Daniel. I hadn’t noticed that setting.