You must double click the linedef that you want to edit texture and not try to click that box thing.
Just don't use Workbench, because it's not done? SRB2DB and SRB2DB2 are better options. You should try SRB2DB first, though, as it builds nodes without error on large maps unlike SRB2DB2.
Just don't use Workbench, because it's not done? SRB2DB and SRB2DB2 are better options. You should try SRB2DB first, though, as it builds nodes without error on large maps unlike SRB2DB2.