I'd love, if the plugin would support stacking of temporary group memberships.
So when I add someone to group premium for 1 week (addtemp) and then, on the next day, I add the same player to group premium for another week, that this player is in group premium for 13 days from now on (because one day is already over).

https://github.com/lucko/LuckPerms/wiki/Configuration#temporary-add-behaviour

or

https://github.com/lucko/LuckPerms/wiki/Command-Usage#lp-usergroup-usergroup-parent-addtemp