Set default stroke Line width
It would be useful to be able to set a new default line/stroke weight or set it before you star drawing. Currently the option in the side menu only appears once you have started a line and resets when you start a new layer. I almost always need a 0.25 weight yet have to constantly either start a line and go back and set from 1 back to 0.25
There are two ways to address this problem.
1. Per document.
Create a line or a rectangle, press D to reset the appearance to the default one, and then apply a stroke weight you want. Then open the Graphics Styles panel and drag-n-drop you shape with the proper weight over the [Default] style in the panel. This will force this appearance to be applied to all new objects in a document, when D is pressed.
2. For all new documents
Locate the folder with document profiles.
On Windows it should looks something like
C:\Users\[username]\AppData\Roaming\Adobe\Adobe Illustrator 26 Settings\[language, like 'en_US']\x64\New Document Profiles
On MacOS it’s somewhere here
Users > [user account] > Library > Application Support > Adobe > Adobe Illustrator 26 > [language, e.g. 'en_GB'] > New Document Profiles
Open the profile you want to change (I use Print and Web).
Repeat the same steps as above, delete the shape you used to override the default graphics style and save the document.
If Illustrator forbids you to do it, save it elsewhere and then replace the original files.
Now all new documents based on a certain document profile will have the default weight you defined.
This method can be also used to change default swatches, default fonts, etc.
Don’t forget to backup you document profiles, because Illustrator tends to overwrite them on update.
Marc Bruns commented
Isn't there some settings file we can update that has these settings?
Shane Weber commented
agree come on Adobe.
Same here! I would like to add 0.35 and 1.5 to the list of default stroke widths in Illustrator. They are needed frequently when creating pen-and-ink–like scientific illustrations in Illustrator. For now I've resorted to saving graphic styles for each stroke width, including tapered and variable width adjustments.
Allard Meijer commented
yes i agree and i would also like to have customized line weights, so for instance that i can put 0,18 in there