Hey Sean Welcome to the Forum!
You can start this by creating a new data type called “WeighIn”. Within the WeighIn data type, there could be a field called “Weight” (Type: Number, List: No). By default there will be a Created Date field (date), but if you’d like the User to be able to select a custom Date, then you can have a second field called “Date” (Type: Date, List: No).
On the page itself, add an input (set the type to decimal or integer) for the Weight field, and add a date/time input element for the WeighIn’s date. Then place a button next to those which will be responsible for creating the WeighIn entry (Thing) in the database.
For example, when Button “Submit Weigh In” is clicked, the action is: Data --> Create A New Thing --> Thing: WeighIn
“Weight” = Input weight’s value
“Date” = Date/Time Input’s value
Then add a second action --> “Reset relevant inputs” to clear the data from the inputs.
Once you’ve tested this once in preview mode, you can go to the Data tab --> App Data --> WeighIns and the WeighIn entry will show.
If the User is logged in, the Creator will automatically be stored as this User.
If you’d like to view a User’s WeighIns, there are a few ways to do this - but most simply would be to have a repeating group. The type of content would be WeighIn, and the data source would be Do A Search For WeighIns, with the constraint being Created by equals Current User. Sorting the results by Created Date descending = yes sorts the results from Newest first to Oldest. (Selecting descending = no would sort the results from Oldest to Newest).
Place two text element insides the repeating group cell to display the weight and the date text fields for each Weigh In. This could be displaying in any way you prefer, but the dynamic expressions would be “Current cell WeighIn’s Weight” and “Current cell WeighIn’s Date”.
If you have any questions feel free to ask and we can definitely assist. There are more ways that the above to display and compare the data, but this would be one way to get started.