It is possible that a change in screen resolution has caused the columns in the Data and Network Model Manager to appear wider than intended. To solve this problem, open the User Settings (e.g. menu Tools-> User Settings) and click on the "Reset Column Widths" located at the bottom of the page Data/Network Model Manager.

Since version 2024 SP3, there is an additional option to "Resize Width to Content" when right-clicking on the column headers in the Data or Network Model Manager.