TapNoiseSticky Keys lets you enter shortcut modifiers in sequence instead of holding them all at once. It can help when a multi-key combination is difficult to press simultaneously.
Turn it on deliberately
Find Sticky Keys in System Settings › Accessibility › Keyboard. Review its options, including any sound or on-screen feedback, before testing a familiar shortcut in a disposable document.
Start with Copy: select a harmless word, use the modifier sequence and verify the result by pasting elsewhere. A clear test is better than discovering the behaviour during a destructive action.
When a modifier seems stuck
If typing unexpectedly selects text, opens a menu or triggers commands, check whether Sticky Keys is enabled. Also inspect the physical keyboard and any remapping utility; Sticky Keys is not the only possible cause.
If the Mac is shared, confirm whether another user depends on the feature before turning it off. Each accessibility setting should be changed for a reason, rather than reset as part of a blanket keyboard cleanup.
Learn the action separately
Sticky Keys changes how you enter a combination, not which command the app assigns to it. The app’s menu still shows the current shortcut. TapNoise’s optional shortcut sheet can display those menu commands when you hold Command.
For finding unfamiliar menu symbols, read learning Mac shortcuts from menus. If the modifier positions themselves are awkward, remapping Command and Option addresses that separate issue.