PROBLEM:
Every time an editor trims the in point of a clip that has keyframes at/near the in point, those keyframes lose their positioning relationship to the clip's in point: trim inwards and keyframes are trimmed out of view in the ECP, trim outwards and the keyframes no longer apply to the beginning of the clip as intended. The same problem applies when trimming a clip's out point with keyframes at/near the out point.

SOLUTION:
Keyframe pinning checkboxes in the ECP would allow keyframes to move together in unison with a clip's in and/or out points when trimming a clip in the Timeline. (see illustration)

In point checked: with the In point checkbox checked, all keyframes would move along with the clip's in point when trimming.

Out point checked: with the Out point checkbox checked, all keyframes would move along with the clip's out point when trimming.

In+Out point checked: with both checkboxes checked, only the keyframes in the first half of the clip would move when trimming the clip's in point. Likewise, only the keyframes in the second half of the clip would move when trimming the out point. NOTE 1: Users would be allowed to trim a clip up to the point that any two keyframes collide. For example, if there are 2 Scale keyframes 30 frames apart near the center of the clip, one in the first half and the other in the second half, the user would only be allowed to trim the clip's in or out point inward up to 29 frames since at that point the two keyframes would be bumped up against each other. NOTE 2: checking one or both checkboxes could also serve as a method of preventing keyframes from moving when slipping a clip. This could effectively replace the need for the following FR in which I suggest using a Keyboard modifier to control whether or not keyframes move with the clip when slipping: https://adobe-video.uservoice.com/forums/911233-premiere-pro/suggestions/38075233-slip-clip-keyboard-modifier-that-would-make-a-hug

Neither checked: with neither checkbox checked, keyframes would behave the way they currently do: staying put when trimming, or moving when slipping the clip.

FINAL NOTES: The checkboxes should be 'sticky', meaning that when a user switches clips in the ECP, closes and reopens a project, or even creates a new project, the last used checkbox setting should remain. Since users would probably want their keyframes to stick most of the time, it would probably be best to have these 2 checkboxes checked by default when first using Pr.

As always, thanks for listening!