I want to keep the same line width but specify a much longer dash.
The symbology controls in QGIS 3 have changed significantly from 2.X, so the many answers re: line symbology control for QGIS 2.X are now obsolete.
When I attempt to edit the settings using the button-dropdown to the right of the
Stroke style field, I invoke an
Expression String Builder that might enable me to customize stroke styles to my heart's delight; but the syntax is not explained.
It looks like it expecting an SQL expression, because it looks like a similar dialog box for managing Attributes. But I cannot find any documentation on how it works. The "Expected Format: string [no|solid|dash|dot|dash dot|dash dot dot]" is cryptic.