No, this is not possible.
Sure you can, just add something like:
dispatch.earliest_time = -15m
dispatch.latest_time = now
to the ui-prefs.conf on system/local to make it global or in /etc/users///ui-prefs.conf
[search]
dispatch.earliest_time = -15m
dispatch.latest_time = now
Great, but is there a way for the users to do it by themselves?
No, changing the config file is the only way
@ddrillic please accept an answer if it solved/helped it and upvote it. Otherwise let us know how can we help further