The selection tool should be able to work with keyframes and layers seperately.
The selection tool is capable of doing far too many thing concurrently. On the timeline, it can select text, select layers, move layers, select keyframes, move keyframes, and more.
For this reason, a selection marquee intended for keyframes can only be drawn if the user begins clicking and dragging from a grey section of the timeline. (But NOT if that is the text area for an expression!) This must be very carefully done, since it will otherwise result in layers being moved accidentally.
I propose that a preference be added, which, if enabled, would require the user to hold down a modifier key to switch the selection tool into "keyframes-only-mode."
(Though, I'm not sure if any modifier keys are still available for that purpose. CTRL perhaps?)
This is ID # 9 in my features spreadsheet: https://docs.google.com/spreadsheets/d/1dVJb7kI_ZETLavrplfARgn9gL8HUpvkq6A0jCPxqA3w/edit#gid=1839895625