Merging Multiple Google Slides Presentations into One: A Step-by-Step Guide

You can indeed merge multiple Google Slides presentations into one, and it's typically more convenient to do this in the cloud rather than downloading all the presentations to your local computer.

Here's a step-by-step process on how to do it:

1. Open the main presentation where you want to merge all the other slides.
2. Click on the slide in the left panel where you want the other slides to follow. If you want them at the end, click on the last slide.
3. Go to the "File" menu.
4. Select "Import slides...".
5. In the import window, select the "Google Drive" tab if it's not already selected.
6. Navigate to the shared drive folder where the other presentations are stored.
7. Click on one of the presentations you want to import and click "Select".
8. You'll then see a new window showing thumbnails of all the slides in the presentation you selected. If you want to import all the slides, click "All". If you only want some of them, click on each slide you want to import.
9. Make sure "Keep original theme" is checked. This should preserve the background and formatting of the imported slides.
10. Click "Import slides".
11. Repeat this process for each presentation you want to import.

This process should retain all backgrounds, formatting, and content of the imported slides. If you're still having trouble with some backgrounds not being imported, it may be because the backgrounds were set as master slides. In this case, you would need to go into the original presentation, go to "Slide" > "Edit master", and then copy the background from there. Then you could paste it into the master slide of the main presentation.

Remember that because this process involves copying slides, any changes made to the original presentations after the copy will not be reflected in the main presentation. If you want to maintain a live link to the original slides, you would need to use a different tool or extension that supports this functionality.