I'm also new to UltraWidescreen 3440x1440.
In User Settings I changed the uiHorizontalFrameScale from its current =0.93889 to =1.3 (simply because previous to the 1.21 update I had changed it to 1.3 from its then 1, and I assumed I should do the same again).
Don't know if I should have or not, but everything seems to be still working okay although I also get the same side thing as you show in your image.
Anti-Hero wrote:
Thank you folks for the 21:9 help. I'm new to ultrawide and caught something in Witcher 3 that googling didn't shine any light on. Has anyone else experienced this bug? I browsed the thread and saw no mention of this, so I didn't know if it's unique to patch 1.21 or not.

When pinning formulae the list is pushed out of the crafting UI safezone. I did a little MS paint arrow to point where I believe the pin should be. Any ideas?