I had a stroke several months ago and have a hard time holding down the shift key for image editing in gimp like I used to do. I thought I'd try using sticky keys but every time I click it lets off the shift or ctrl. Is there a way to have it persist until I press the shift / ctrl key again?
In Windows 10 and Windows 7 (I believe), in the control panel under Keyboard, it is possible to select the additional sticky keys option "Lock the modifier key when pressed twice in a row". I think this is what you are looking for.
Assuming you are using windows, a double press of the control, alt or windows key locks that modifier. Another press of that modifier releases it. Shift is more complicated. You need to press right then left shift in turn to lock shift. Pressing left shift clears the shift lock. This shift lock is different to caps-lock because if shifts all keys, including the numbers. The sticky-keys icon in the task bar shows modifier key status.
On a Mac, shift, command, control and option all work the same: one press to modify the next key, two presses to lock the modifier and three presses to clear the modifier. As with windows, modifiers combine to work together. When enabled, modifier key status is reported to the screen momentarily.
Both systems can be configure to play a sound to indicate modifier key activation.