Thanks for reaching out to us.
Would you mind sharing the version of Photoshop Elements and your computer's OS?
Please follow the following steps to set the UI scaling for a 4K display right:
1. Open Preferences by pressing Ctrl /Cmd + K
2. Go to Display and cursors tab from left panel of preferences dialog
3. Under High Density Display section, change the UI scale factor option to suit your case best
4. Click Ok and restart the application for changes to come into effect.
Let me know in case of any queries.