Changing who a plot lists HyperPlots

effectadd <who> to plot at <location>HyperPlots

Put a player on the plot's list of members, who may build while an owner is online

add arg.1 to plot at player's location

effectadd <who> to plot at <location> as trustedHyperPlots

Put them on the list of trusted players, who may build at any time

add arg.1 to plot at player's location as trusted

expressiondeny <who> from plot at <location>HyperPlots

Put them on the list of players who may not come in

deny arg.1 from plot at player's location

effectremove <who> from plot at <location>HyperPlots

Take them off all three lists

remove arg.1 from plot at player's location

expressionplot claimed at <location>HyperPlots

True where there is a plot that somebody owns

if plot claimed at player's location:
    send "&7Somebody owns this plot."

Guide and examples

command /letin <target:offline player>:
    trigger:
        if owner of plot at player's location is not player.name:
            send "&cThis is not your plot."
            stop
        add arg.1 to plot at player's location
        send "&a%arg.1% may now build here while you are online."

command /trustin <target:offline player>:
    trigger:
        if owner of plot at player's location is player.name:
            add arg.1 to plot at player's location as trusted

command /keepout <target:offline player>:
    trigger:
        if owner of plot at player's location is player.name:
            deny arg.1 from plot at player's location

command /unlist <target:offline player>:
    trigger:
        if owner of plot at player's location is player.name:
            remove arg.1 from plot at player's location

command /free:
    trigger:
        if plot claimed at player's location:
            send "&7Somebody owns this plot."
        else:
            send "&aNobody owns this."

Syntax	Effect
`add <who> to plot at <location>`	Put a player on the plot's list of members, who may build while an owner is online
`add <who> to plot at <location> as trusted`	Put them on the list of trusted players, who may build at any time
`deny <who> from plot at <location>`	Put them on the list of players who may not come in
`remove <who> from plot at <location>`	Take them off all three lists
`plot claimed at <location>`	True where there is a plot that somebody owns

The player need not be online, but must have played on the server before.
Somebody is on one list at a time: adding them as trusted takes them off the members and off the denied.
These change the plot the way PlotSquared's own /plot add, /plot trust, /plot deny and /plot remove do, without asking who runs the command: check the owner in the script, as the examples do.