Decreasing the file size does not work

See if this works.
Remove All Unused Media

Armin said:
3) Then via "Save as"  Ive saved it in another file..

 Save not Save As. Save should change (delete) the files in that document.

Armin That's odd since we have no other reports of this. I've tested this on my own system and confirmed that it does work.

ScreenFlow 9.0.3 on macOS 10.14.6 or 10.5.5? 
Can you confirm that?

Armin You could send me one of your projects (smallish) via a link and I can test on my system.

Armin I looked at the file you sent which includes screen recording and webcam. The media folder shows only the .scc file so there's nothing to delete.

Armin 
I did my own test.

1. Open ScreenFlow and do a Screen Recording.
2. Save.
3. .scc is in the Media Folder.
4. Do a Second Screen Recording adding to the current document.
5. Save.
6. Both .scc are in the Media Folder
7. The Second Screen Recording is not in the timeline. I use Delete Unused Media and a popup window shows the Second Recording and on Delete confirms it can't be undone and I delete the Second Screen Recording.
8. Save.
9. Quit ScreenFlow
10. Check Media Folder and Second Screen Recording .scc is still in the Media Folder (along with the original).
11. Conclusion: Unused media was not deleted.

This is an issue.

Second test with imported media

1. Open ScreenFlow and do a Screen Recording.
2. Save.
3. .scc is in the Media Folder.
4. Imported MP4 file
5. Save.
6. scc and MP4 are in the Media Folder
7. The MP4 is not in the timeline. I use Delete Unused Media and a popup window shows the MP4 and on Delete confirms it can't be undone and I delete the MP4 file
8. Save.
9. Quit ScreenFlow
10. Check Media Folder and in addition to the .scc file the MP4 file is still present
11. Conclusion: Unused media was not deleted.

This is an issue.

Armin I can confirm your report is correct in that ScreenFlow does not delete Unused Media from the Document. It makes no difference whether the unused media is a screen recording or imported file.

Please do fill out the form and also mention that I've tested and confirmed the issue as well.

Armin said:
Couldn't you report the bug, please? I am only a simple user, nothing more.

 The engineers may want to contact you. Different systems behave differently. If they fix it for my system it may not be fixed for yours.

Armin said:
May I further ask, where the differences was between your first tests (where you meant, that everything works fine) and the latest test?

 I'm not sure which is why they may need to speak to you. They may need to see if there's another variable.

If you fill out the form, you'll get a case number. You can post that here. Then I can add details from my testing to your case.

The engineers tend to want to hear from customers or they may feel it's a low priority if customers haven't reported this.

Armin said:
Case number: 00751692

 Thanks for that. I'll track and make clear my verification.