to know which tools allow to customize QGIS's interface
To customize the QGIS interface, go to the Settings menu > Customize Interface. Also have a look at the options available in the Settings menu > Options.
The customization options should be mostly self-explanatory. See the interface customization section of the QGIS Manual for more details.
You will need to build an attribute expression in the Filter widget:
So basically: <<YOUR_USERNAME_FIELD>> is *USERNAME*
The custom code below will replace *USERNAME* with the currently logged in user's username.
You will need to alter two of the functions in Filter/Widget.js.
These lines in PostCreate() will get the current Portal username:
If you work with timeseries, Postgis now have a native way to handle these: trajectory (it's based on LINESTRINGM, you can see for example in the link or in the first function you should use: ST_IsValidTrajectory).
It does not have a lot of function (in my opinion), but in my understanding it can answer your problem. Once you have your lines transformed ...