How to make a Projects & Tasks Manager with Google Apps Script

I borrowed 'my' Projects & Tasks Manager from Ilya Mikhelson because of his use of the Google Spreadsheet's formula Sparkline() for the timeline of the manager.  The formula is not the easiest one. The 'onion method' of Ben Collins helped me to understand it.

=SPARKLINE({INT(B4)-INT($B$2);INT(C4)-INT(B4)};
    {"charttype"\"bar";"color1"\"white";"color2"\IF(E4="Done";"LemonChiffon";
        IF(today()>C4;"OrangeRed";
            IF(AND(today()>B4;today()<C4;E4="To do");"Orange";
                IF(AND(today()>B4;today()<C4);"Yellow";"Chartreuse"))));
                    "max"\INT($C$2)-INT($B$2)})

'My' Projects & Tasks Manager makes a folder and a (gmail) label on spreadsheet and sheet (project) level. It also makes a contact group on sheet (project) level.

Every project (sheet tab, some sheet rows, folder) has its own color.

The Projects & Tasks Manager can be downloaded via this link. Make a copy and check the script before you use it (via the menu for which a trigger must be added)

My 'learning moments':

• the data part of the SPARKLINE formula {INT(B4)-INT($B$2);INT(C4)-INT(B4)}
• Session.getActiveUserLocale() and the LanguageApp to replace the name of the first sheet which name is in the language of the user
• Math.floor((Math.random() * n) + 1) to choose a color for the project.

Other sources of inspiration:

• Change Google Drive Folder color with Apps Script, Stéphane Giron, 3 may 2019
• G Suite Solutions — Apps Script Powered Workflow Automation, Laura Taylor, 12 March 2020

UPDATED 05-05-2020