Feature suggestion:

• If two adjacent clips come from the same source, and the first frame of the clip to the right is the same frame that you'd get if you extended the clip to the left by one frame, then the boundary between the clips is rendered in a different colour. This doesn't prevent them from being worked with as independent clips, and if they aren't exactly adjacent on the same track, this highlight does not occur.
• If the highlighted region is double-clicked, then the two clips are joined back into one clip. Because of the relationship in the first point, if you take the first clip and extend it right to include the length of the second clip, it will generate the same frames as the second clip, and so it can replace it.
• If the clips have identical effects, then the resulting "joined" clip gets the same effects. If the clips don't have identical effects, then a dialog should appear with buttons to permit the user to choose between left only, right only, left before right or right before left. In the latter two cases, the joined clip gets all the effects from one clip followed by all the effects from the other clip, as though you had copied one clip and then used "Paste Effects" on the other clip. (I do not imagine this would typically be the desired end-state, but the user might want to edit a new stack of clips using some from the left and some from the right, without having to rediscover all of the parameter values.)

The feel of this operation is intended to be similar to the transition in edit state that occurs if you use the Undo function immediately after cutting a clip.