Note: I'm not very familiar with the GUI~EDitor and the built-in code stuff...
if there's no GUI~Editor text box for changing the "you can go's: prefix" text (but, I believe there is, along with the toggles which you already know of/mentioned), you're going to have to dig into the underlying code, trying to find the code that handles it (be warned that these changes are global, you can completely mess up your game, while it can be fixed up, it's not easy as you'd be the only one knowing what you did, but don't known how to undo it, while those who could help you undo it, would have a hard time in trying to have you try to explain what you've done, to undo it. Note that via doing this through the GUI~Editor, forces you to click on 'copy' which protects the quest program itself from being messed up, but that doesn't protect your game file from being messed up), if you wish to try to find the code involved with the 'prefix' stuff:
Filter (bottom left corner, very very bottom of the 'tree of stuff' ) -> show library elements -> (toggle this on, have it be checked/on) -> above in the tree of stuff, you'll now be able to see all of the underlying (built-in) code stuff as light grey text, good luck with trying to find the code that handles the 'prefix' stuff...
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with the more current version, we got a lot of added features, and because there's so many tabs for these features, they're no default as toggled off, so not to be cluttering up the GUI~Editor, see the version history here:
http://docs.textadventures.co.uk/quest/ ... notes.htmland the major control features are found here:
global options/settings:
'game' Game Object -> 'Features' and 'Room Description' Tabs -> (see the various feature options of/within these two Tabs)
local/specific/individual options/settings:
'whatever' Room Object -> 'Setup' Tab -> 'use default prefix and suffix' toggle option/setting
'whatever' Room Object -> 'Room' Tab -> the two text boxes at the top (description prefix and objects list prefix) options/settings
'whatever' (non-room) Object or Player Object -> 'Setup' Tab -> 'use default prefix and suffix' toggle option/setting
'whatever' (non-room) Object or Player Object -> 'Option' Tab -> (various options/settings)
'whatever' (non-room) Object or Player Object -> 'Features' Tab -> (various options/settings)