Lost Dashlets and Tabs for one user

I don’t understand what you pasted there.

But the general idea is this: work with the array in PHP, after it is unserialized an decoded.

Your code can be based on this function, I believe:

https://github.com/salesagility/SuiteCRM/blob/932b87108edc154dd3c9c86b57ceaa24acd40835/modules/UserPreferences/UserPreference.php#L391