Regular react to open allows for one reaction, the emote of which can be changed with the setemote command. This page is about the premium-only feature of having multiple reactions on the same react to open.
Multiple reactions requires having Stick Premium on your discord server.
Open the webpanel and select your server. Scroll all the way down to the REACT_TO_OPEN_EXTRA section:
Fill in what you want to be different for the extra reaction you want to add.
For example, change the staff role or the opening message that gets sent at the start of a ticket.
Extra reactions will use the default settings (as seen on the rest of the same page) for opening up tickets.
The difficult part of this is setting the emote to something valid. This has to be either the unicode variant of an emote, or the name/id of a custom emote in the same discord server. You can get either of these by sending the emote in some chat, editing the message, and putting a backslash (\) in front of it.
In the case of a custom emote, it will change it to <emote-name:emote-id>, these are the easiest to use.
Once you have filled out everything, press the "add extra reaction" button, and press save on the top right.
Give Sticky about 30 seconds to update, and use the createreact command to test if it worked!
Manually edit the REACT_TO_OPEN_MESSAGE further up and add your new emotes. Sorry, this can not be automated in a nice fashion.
For the emotes you should always use the full text presented by the \emote trick mentioned above.
Made a mistake and want to start over, with no extra reactions? Put "" in the "Raw" section and press save.
The Raw section contains the raw JSON of the extra reaction, you can change anything you would like in there. You can of course also just delete everything and start over again if you are not comfortable with JSON
The only limits are the limits set by Discord. You can have up to 20 different reactions on a single message.