Suggestion:
GUI to accept, decline quest and to left quest, max quest at same time, i mean, to force the player to no carry 208348092309 quest at same time, and to limit it to a custom number, for example, max 10 side quest at same time, and let the player to accept/decline/left quests, i know is possible via event, but if it is integrated in the plugin should be more cool.
This is more like a evolution from my old suggestion,
For the accept decline gui i mean something like this
and for the "leave" quest i mean in the quest log, a button to leave active quests to let space to other quest