First off. One of the best addons ever! However... in my efforts to learn lua, I wanted to reverse the 'shift key' operation to see if I could figure out how to do it. Works fine except for util.lua, which might be outside the scope of my testing anyways. Minus the commented notes, just 3 entries, though longer with the added toggle.
Anyways... knowing that I've not interacted with you or the other contributors before, I'm sure this is quite random. Apologies if I've overstepped in anyway & thank you for reading :)

Result:

InteractiveWormholes:
Modifications to toggle the 'shift key' operation:

..providers\gossip.lua line 54-57
-- if IsShiftKeyDown() or C_PlayerInteractionManager.IsInteractingWithNpcOfType(Enum.PlayerInteractionType.TaxiNode) then
-- check shift button interaction
if (addon:GetOption('nshift') and IsShiftKeyDown()) or (not addon:GetOption('nshift') and not IsShiftKeyDown()) or C_PlayerInteractionManager.IsInteractingWithNpcOfType(Enum.PlayerInteractionType.TaxiNode) then

..\util.lua line 98-102
-- check shift button interaction
-- if IsShiftKeyDown() or InCombatLockdown() then
if (addon:GetOption('nshift') and IsShiftKeyDown()) or (not addon:GetOption('nshift') and not IsShiftKeyDown()) or InCombatLockdown() then
--original -- we'll never be active if the user holds shift or if the player is in combat
-- if 'nshift AND shift key toggled' or if the player is in combat

..\settings.lua
--added entry to options menu
{
key = 'nshift', --added to invert shift button interaction
type = 'toggle',
title = L['Default shift key operation'],
tooltip = L['Toggle to reverse shift button up/down for addon'],
default = true,
},

was trying to setup a separate function to call on, but I kept doing something wonky & ultimately had to use the rather long line of code in gossib.lua and util.lua
--kept getting a global error from util.lua---forgot to comment out the original edit...either way, leave it to actual author
--if they want it in
--gossip.lua
function addon:ShiftDown()
if (addon:GetOption('nshift') and IsShiftKeyDown()) or (not addon:GetOption('nshift') and not IsShiftKeyDown()) then
return true
end

So you want an option to disable the shift key disabler?

The code just reverses the shift key operation. Hold shift to enable the addon vs the default. In many ways, this addon is a blessing, but there are also times when I know which dialog click will get me where I need to go. Coin flip on the visual display that IW brings vs the other addons that I find to be useful as well, but then everything winds up on the same map... thus, I find myself holding shift on enough occasions to get back to the dialog 'if I know what cryptic option' I need to select. Anyways, that was a bit wordy, but.... I found that having the option to reverse the shift key interaction to be a solution, though I'm sure someone else would be much better at coding it. Either way, it was a lua learning experience, if you think it's something you want to add to the addon, those are the notes for what worked for me. If not, no worry, it's your creation and I respect that.