Launch WurmOnline from desktop, login etc...
Open settings
Swap to the key bindings tab
Activate a textbox element in the key bindings tab
Open another window (inventory, console, etc) (only tested inventory and console with F1, F3 default keybinds)
The keybind textbox will now remain on screen until the game has closed.
The on screen textbox ui element can be interacted with even while the settings window is closed.
Clicking the save button after changing a keybind in the key bindings tab appears to prevent textboxes from lingering.
https://imgur.com/g9QYopp