I've been looking for a way to clear or disable the Timeline myself with no success. Perhaps Timeline items go away only when you move the files off the device(?)...
Unfortunately the "My Files" "Timeline" content is actually controlled by another process called "Media Storage" (this process scans all the files on the device looking for pictures, music, and other content then it builds a database so the system or apps such as music players can quickly find the content, it usually runs on boot-up and can update occasionally.
The only way to clear (or temporary clear) the timeline content is to clear the "Media Storage" database, by clicking "Force stop" and "Clear data" on the Media Storage process, though if you do this it will just rescan again eventually, and if you turn it off or prevent it from scanning you can loose access to your ringtones / alarms and other system sounds , also any music files on the device as a lot of applications use this service (otherwise everything would need to scan the memory card ./ memory for files causing increased cpu overhead and device lags....)...
See screenshots.
The only way to clear (or temporary clear) the timeline content is to clear the "Media Storage" database, by clicking "Force stop" and "Clear data" on the Media Storage process, though if you do this it will just rescan again eventually, and if you turn it off or prevent it from scanning you can loose access to your ringtones / alarms and other system sounds , also any music files on the device as a lot of applications use this service (otherwise everything would need to scan the memory card ./ memory for files causing increased cpu overhead and device lags....)...
See screenshots.
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Figured it out
Plug tablet into the computer. Rename the folder that you don't want showing up with a '.' in front of it. I.e. "Adult" to ".Adult".
Then install Astro File manager, change the settings so that you can view hidden folders. And then you can still access the folder from the tablet, but will not show up in Timeline or the stock file manager.
Plug tablet into the computer. Rename the folder that you don't want showing up with a '.' in front of it. I.e. "Adult" to ".Adult".
Then install Astro File manager, change the settings so that you can view hidden folders. And then you can still access the folder from the tablet, but will not show up in Timeline or the stock file manager.
you might also be-able to add a .nomedia file to the folder too this is supposed to prevent the media scanner from scanning the folder contents, though it doesn't work on all devices and I haven't tested it with timeline. or samsung yet., thought I would throw it out there if anyone wants to test.
At this time it's still unclear if you can hide items or completely remove the from the recent items list, with out moving every little file and or download and the list will only repopulate as you continue to download or add files. Just tap the added date above each subsection and collapse each individual section. While this isn't a permanent fix and the list will repopulate once you reopen the My Files app, it's only a minor inconvenience for someone who uses the app occasionally. 
