Adding / altering custom properties on toolbox parts can be interesting. I'd recommend doing it through the Toolbox Settings utility you'll find in the from the program menu ...>Solidworks 20xx>tools.
Here's a good video on configuring the toolbox Configuring the SolidWorks Toolbox - YouTube
If you're going to make changes to the toolbox, make a backup first.
I got this file from anybody else, so it is not part of my toolbox.
Now I tried to add this file to the Toolbox Settings Utility, but also there it did not show the name I see in the drawing.
Here you can find the file: http://transfer.samsoft.at/Skt-Schraube_M12x60_ISO4017.sldprt
Seems it is a word from other language. At the time of installation, have you selected English language or no ?
His screenshot shows German language in his SW. "Brennenung" is German for "Designation" or "Description".
To figure out where the name for the item in that column comes from, select the column and then select the equation icon.
That will tell you where the column gets it's fields.
As far as the header for the column, that is just saved in the template. You can change that to whatever you wish.