You will have to hack the code (vm/soy files) in the JIRA Installation to change the "More" and "Assign" buttons (if you are talking about the system menu buttons).
Note: You can hide the native "Assign" button if you wish https://confluence.atlassian.com/display/JIRAKB/How+to+remove+the+'Assign'+button+from+issues
Can you explain more about what you are trying to achieve here? It is correct that these buttons are not translatable through the InProduct Translation plugin but there may be another way to deal with the Assign option by moving it to a workflow action where you can give it any name you like.
Unfortunately I do not know of a similar trick for the More button.
Hey team! I'm Cameron Deatsch, Head of Server at Atlassian. At our European Summit just a few weeks ago, I spoke about the latest regarding our Server and Data center products and o...
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG
You're one step closer to meeting fellow Atlassian users at your local meet up. Learn more about AUGs