Quick answer: GameMaker game tween paused globally affecting per-instance tweens? Default tween system pauses all - track per-instance pause state.
Pause menu opens; UI tween should stop; gameplay tween should also stop. Both pause; can't differentiate.
Per-tween pause flag
Each tween has an 'paused' state. Pause some; leave others. Granular control.
Or tag and resume
Pause all; on unpause, restore only tweens tagged 'gameplay'. UI tweens stay paused or active.
Two tween systems
UI tweens and gameplay tweens in separate libraries. Each has its own pause.
“Pause is global by default. Granularity needs design.”
If pause behavior matters (most games), explicit per-tween pause is the safe design. Document; reuse.