They are also known as 'soft buttons'. I could not find any info about them, so I guessed they are probably shortcut keys. When I added 'shortcut' to the keyword search, I came across an Intel forum post where someone asks about 'the two buttons on top' of Euclid and they were pointed to this page.
This message was posted on behalf of Intel Corporation
Thank you for contacting Intel® RealSense™ Technology support.
Your case number is 03066809
This message is to let you know that we are currently investigating on your request related to your Intel® Euclid™ product.
As soon as we have any updates we will be contacting you back.
Thank you for your patience and understanding on this matter.
Intel Customer Support
I have received an email claiming that the issue has been closed a few days ago but the results have not been posted. Can you check it out please?
As far as I know, my answer above about the shortcut programming was the correct one, as it was the solution advised by another Intel support agent when someone else asked how the top buttons on the Euclid could be programmed.