How To Select Multiple Slides
In Google Slides
Open your Google Slides presentation.
In the left panel, hold down the Ctrl key (Windows) or Cmd key (Mac).
Click on each slide you want to select.
To select a range of consecutive slides, click the first slide, hold Shift, then click the last slide in the range.
The selected slides will be highlighted.
You can now move, duplicate, or delete them as needed.