Is it possible, and if so how, to display a variable on a form? I have a form on which I want the user to be able to enter a value to be used in a calculation (e.g. a percentage), but I don't want this value to be stored in the database, only the result of the calculation. Can I do this? Thanks.
Nope, that isn't possible. You need to store the variable in a metaobject if you want to display it in a form.
However, what you can do is calculate the value in a Microflow (I assume you're already doing this) and then include a "send text message" Activity in the flow:
Create an activity
Double-click it to select the type of action
Select "Send Text Message", which is under "Client"
You can fill in any microflow expression which will be shown in a little popup box when the microflow executes.
See this thread for more info on handling user input with forms and microflows.