Over a year ago, when I was working on the patterns for 622, I found that drawings imported from OnShape into InkScape consisted of many individual line segments. There had to be a better way, and Craig Townsend has found it. Here for future reference, is a YouTube video that makes it dead easy.
Thanks Craig!
Update January 22, 2024. This tutorial is out of date. With newer versions of Inkscape the same process is simpler, but I keep having to figure it out again. So here are the steps:
- Ungroup until you have individual paths
- Combine all the simple paths
- Select the Node Editor tool
- Select all the nodes
- Click the join nodes button
Pembroke:87 
Glad I could help. I’ve got to pay you back for all the help you have given me from when I started my initial designs to now. I checked out that guys channel, and he has a few more methods that might be worth trying. The 3rd attempt looks the easiest.
Craig
Thanks Craig, I’ll have to check it out!
How many times have I watched this video? Like every time!