You could create an adaptive card and send it to the manager through a Teams message. This would allow for the option to choose multiple items. Although, it would be much easier to just send the link to the item and ask the manager to choose the options. You can have the flow trigger when the item is updated, and use the check for changes action to see if the field has been modified.
If you go the adaptive card route, this is an example of the code for an adaptive card:
{
"type": "AdaptiveCard",
"body": [
{
"type": "TextBlock",
"text": "What apps are required?",
"weight": "Bolder",
"size": "Medium"
},
{
"type": "Input.ChoiceSet",
"id": "requiredApps",
"style": "expanded",
"isMultiSelect": true,
"choices": [
{
"title": "Acrobat",
"value": "acrobat"
},
{
"title": "Word",
"value": "word"
},
{
"title": "Excel",
"value": "excel"
},
{
"title": "PowerPoint",
"value": "powerpoint"
},
{
"title": "OneNote",
"value": "onenote"
}
]
}
],
"actions": [
{
"type": "Action.Submit",
"title": "Submit"
}
],
"$schema": "http://adaptivecards.io/schemas/adaptive-card.json",
"version": "1.3"
}
It produces this:
