The only solution that worked for me (Windows 10) was to open the registry with regedit and expand HKEY_CURRENT_USER > Software > MakeMusic > Finale26 > Finale > Dialog Location. The EditSysMargins...
Or Ctrl-Spacebar (in Windows). You can find this listed in Tools > Lyrics > Lyrics Window, and click on Text. However, there is one gotcha to be wary of: in some fonts the hard space is not a hard ...