Seeing that the new Travel Distance tool has been added to Revit 2020 (which is a fantastic addition), it would be great to see a similar tool created for a continuous Membrane Layer line. The ideal scenario would be a "polyline" type of tool that you can click a start point and continue around corners, etc. This can also be tagged and you can apply linestyles to it. At the moment, to reduce the use of pointless detail lines (which can't be tagged), I have developed a Line Based Family (which can be tagged) that can stretch in the model, but you then have to copy it, move it and rotate it if you want to continue the line at an obscure angle around an element.