sw_urdf no joint axis

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Hello everyone!

I'm trying to export a robotic hand from Solidworks to URDF.

Some of the joints are missing their axis:

I can set the axis coordinates but I don't know to what. Is there a way in Solidworks to find that out?

The drop down menu for the axis didn't provide an appropriate axis which I could use:

If I cannot find the coordinates of the axis, is there a way to add an entry to this menu?

Thanks in advance!