iMove temporary movie files not getting deleted automatically

I am not sure what you are referring to when you say "temporary movie files". In iMovie 10.x.x the iMovie project remains intact after sharing out the movie, so that you can go back to the project and re-edit and/or share out as many times as you want. Even if you afterwards delete the project, the media in the project still remains in the system, in an Event of the same name that gets created when you delete the project. To remove the media you need to open the Event found in the All Events folder in the media sidebar and delete the media inside the folder. If any of the removed media is being used in another project, it would be removed from that project as well.

You can expand or contract the clips display in your timeline by moving the slider located next to the Settings button that you will find to the right of your screen just above the timeline. The slider gives pretty good control.

-- Rich

O.K. I understand what you mean now.

I am running iMovie 10.1.8 on High Sierra and have just now shared out a test project to a File. The temporary file immediately disappeared upon completion of the share. I have not previously heard of your issue of the temp file not disappearing, unless the sharing process fails to complete. So I am thinking that it is an issue specific to your set up. Is it possible that you have not waited long enough for the share to complete?

You might try opening iMovie while holding down the Option and Command keys, and then selecting to delete preferences in the box that appears. Sometimes that resolves odd behaviors.

Regarding the time line expansion control issue, I tried expanding a 52 minute movie timeline by moving the slider next to the settings button. It did expand quite a bit at the first increment. I don't recall the expansion control capability of prior iMovie versions so can't comment on the extent of any change. But if you say there has been a significant decrease in the expansion adjustment capability, I accept your findings there. When you click the settings button a box will appear that gives an option to adjust the clip size, so that might be a more precise way of getting more detail without a large expansion of the time line.

-- Rich