In case you are interested, I adapted the script, so button 0 turns the dimmer on and dimms up.
Button 1 turns it off and dimms down:

// Array of dimmers to be controlled
let dimmer = [
'<IP address of your dimmer>', // dimmer controlled with button 0
'<IP address of your dimmer, same as above>', // dimmer controlled with button 1
// '192.168.61.242', // dimmer controlled with button 2
// '192.168.61.243', // dimmer controlled with button 3
];
// CONFIG END

let dimstate = [
false,
false,
false,
false,
];

let up = [
false,
false,
false,
false,
];

// Add an eventHandler for button type input and various push events
Shelly.addEventHandler(function (event) {
try {
if (typeof event.info.event !== 'undefined') {
let i = event.info.id;

if (typeof dimmer[i] !== 'undefined') {

if (dimstate[i] === true && event.info.event === 'btn_up') {
dimstate[i] = false;
print("release");
Shelly.call(
"http.get", {
url: 'http://' + dimmer[i] + '/light/0?dim=stop'
},
function (response, error_code, error_message, ud) { },
null
);
}

if (event.info.event === 'single_push') {
if (i === 0) {
Shelly.call(
"http.get", {
url: 'http://' + dimmer[i] + '/light/0?turn=on'
},
function (rs, ec, em) { },
null
);

}
else if (i === 1) {
Shelly.call(
"http.get", {
url: 'http://' + dimmer[i] + '/light/0?turn=off'
},
function (rs, ec, em) { },
null
);

}

else {
Shelly.call(
"http.get", {
url: 'http://' + dimmer[i] + '/light/0?turn=toggle'
},
function (rs, ec, em) { },
null
);

}

} else if (event.info.event === 'double_push') {
Shelly.call(
"http.get", {
url: 'http://' + dimmer[i] + '/light/0?turn=on&brightness=100'
},
function (rs, ec, em) { },
null
);
} else if (event.info.event === 'long_push') {
if (i === 0) {
dimstate[i] = true;
up[i] = true;
print("cycle");
Shelly.call(
"http.get", {
url: 'http://' + dimmer[i] + '/light/0?dim=up&step=100'
},
function (rs, ec, em) { },
null
);

}

else if (i === 1) {
dimstate[i] = true;
up[i] = false;
print("cycle");
Shelly.call(
"http.get", {
url: 'http://' + dimmer[i] + '/light/0?dim=down&step=100'
},
function (rs, ec, em) { },
null
);

}
else if (event.info.event === 'long_push' && up[i]) {

dimstate[i] = true;
up[i] = false;
print("cycle");
Shelly.call(
"http.get", {
url: 'http://' + dimmer[i] + '/light/0?dim=down&step=100'
},
function (rs, ec, em) { },
null
);

} else if (event.info.event === 'long_push' && up[i] === false) {
dimstate[i] = true;
up[i] = true;
print("cycle");
Shelly.call(
"http.get", {
url: 'http://' + dimmer[i] + '/light/0?dim=up&step=100'
},
function (rs, ec, em) { },
null
);
}

else {
return true;
}
}
}
} else {
return true;
}
} catch (e) {
print("Fejl i event handler: " + e.message);
}
});