We have created a possibility of adding extra lines in the Timeline view which will allow you to mark the events (timeframes) that have to be done before or after the flight. The lines are set to follow the green 'NOW' line.
First step in this process is to create a line and name it. You need to go to 'General settings' and in 'General settings' section you will find a 'Timeline additional markers' option. Clicking on this option will open a window where you can choose the name of the line, where it should show vs 'NOW' (h-hours, m-minutes, d-days, etc), and the colour of the line. The line displaying before 'NOW' should be added with a minus sign, e.g. -1m for the line displaying 1 month prior to the green 'NOW' line.
Once you have the definitions created, Leon will add these options in the Timeline view under filter 'Markers' (available by clicking 3 dots in top-right corner of the screen). Depending on whether the section is ticked or not, the lines will get displayed in the timeline view.