Just found out:

• You can set the start point of a symbol in the properties inspector
• There's a "convert to symbol" hotkey
• You can hold enter to play the timeline and release it to stop, instead of pressing twice
• You can click and drag to select frames on the timeline instead of shift-clicking

Also found out:

• CS4 bugs are just as annoying in 2018 as they were in 2009

That CC subscription is looking damn good right now.