I am not fully sure I understand what you are asking. However, before that, have you figured out how this flow will work once it is live? The flow is only going to run on the mailbox of the owner of the flow. If that is you, how will this work? Or are you building this flow for yourself and when you refer to a salesperson tagging the e-mail, you mean when you tag the e-mail?
Of course, there is one other possibility, and that is all of the salespeople have granted you access to their calendars, and you are going to set up a workflow for each one once you get this to work. If this is the case, I would use the trigger When an email is flagged (V4).
Then have each salesperson create folders in Outlook that correspond to the category:
When they want the flow to run, they will move the e-mail to the correct folder and flag it, which will trigger the flow. This will be tedious because you will need to duplicate this workflow for every salesperson and then duplicate it again for as many folders will be needed for your categories.
Otherwise, you will need to use the AI builder feature and train it to get the sentiment from the e-mail and then run accordingly. That is not something I have experience with yet but is a project I am just starting to work on. This is why we're going with the AI approach. This way, the e-mails are sent to a shared mailbox, so it only needs to be configured once.
Of course, maybe someone has figure out a different way to do what you are asking or, as I mentioned, I don't understand your requirements.