This adds four commands to enter a due date date in the format [due:: YY-MM-DD] at cursor (with optional hashtags):

• Due end of this week: set to Friday of this week
• Due end of next week: set to Friday of next week
• Due end of this month: set to last day (or weekday) of this month
• Due after I'm gone: set 100 years in the future, i.e. I'm not doing this

The four options of tags to add correspond to the four commands:

• This week tag
• Next week tag
• This month tag
• Never tag

The 'Last Weekday' option toggles whether 'end of this month' should be the last weekday of the month or the last calendar day of this month.