So this confused me at first because in both my 12.9 prod and 17 test environment, the official size limitation of the Name field is 100 characters, not 20. 20 is the visual size limitation in the list_nr.htmpl file. That determines how WIDE the display field is, not how many characters it will store. The instructions above that refer to MOD and SCH files refer to changing the underlying data tables.
If you want to make the field wider, Edit list.htmpl with web screen painter and, double click on the Name field, change the number, save and publish the file. Done.
But you should have 100 characters to play with for the config item names themselves. You'd see that in Web Screen Painter, Schema Designer. Expand the NR object, scroll down to "name" and you'll see it should be string 100.