Theres now a new feature rolling out: video playback speed controls.

Plex has now added it to the video player on most platforms.

The full list of supported platforms is below.

Video playback settings menu overlaying a paused cooking show scene.

Plex

However, there are some catches.

The announcement also mentioned that playback speed will remain constant in a play queue.

No need to constantly change the playback speed setting.

Source:Plex Forums,Plex Support