Hi, I am a long time Inkscape user and am just now starting to mess around with custom dashed lines and markers. I managed the lines no problem, but am having some issues with getting custom markers to work exactly how I want them to. First my successes: after a bunch of fiddling with the Inkscape markers file (I think due to confusion about the marker IDs), I managed to get a few custom markers working in a new file. The goal of this, however, was to create markers that would be usable to edit existing drawings. In those drawings, however, the new markers don't appear. Also, in the markers drop-down menu, seemingly every individual marker I've used in the drawing appears:



I have 2 questions:

-Why are these extra markers appearing in the drop-down menu?
-Why can't I find the new custom markers I created in my old file, even they are available to use in new files?

Any help or insight would be greatly appreciated. Thank you!

1 - All the custom markers that you make will appear there. You can get rid of all the ones that aren't used on the canvas, by using File menu > Clean Up Document. However, if there are markers that you want to keep, and they aren't used yet on the canvas, you probably don't want to do that. If there are custom markers that you want to keep, you could draw a path and use them on the canvas, for example, outside the page border or in a hidden layer, before you do Clean Up Doc, and they will be saved.

2 - Custom markers only exist in the file in which they are created....unless, as you've learned, you can put custom markers in the markers folder, and have them appear in new files. But they can't be retroactively applied to files that existed before you installed the new markers.

I think you would have to apply the custom markers to the old files, either individually, or I suppose a script could be used to apply them all at once. Unfortunately I don't know anything about writing scripts, so I can't offer anything like that.

Here's another thought. You could open the old files, and try doing File menu > Save a Copy. Then Inkscape will save the new copy with the new custom markers in the markers menu (in Fill/Stroke dialog). You still would need to apply the custom markers to the paths in the old files though.

Edit
Just a clear summary. If the custom markers did not exist when the older documents were created, there's no way to have them magically appear in the old documents. There will have to be some extra steps to get them in there.