LINKTOFORM("Order Details_Form", "Order ID", [_THISROW]) creates a deep link to an Order Details_Form with the Order ID column preset with a reference back to the current row (making the new Order Details row a child of the current row).
LINKTOFORM("Orders_Form", "Customer ID", [_THISROW], "Delivery Address", [Customer Address]) creates a deep link to an Orders form, with the Customer ID column preset with a reference back to the current row, and Delivery Address preset with a copy of the customer's address.
LINKTOFORM( view-name, column-name, column-value[, column-name, column-value]...[, app-id] )
view-name - An expression that gives name of the target view. The view named must be of type form.
column-name - An expression that gives the name of a column of the target table.
column-value - An expression that gives a value for the column named by the immediate-preceding column-name argument.
app-id - An optional expression that gives the ID of the app containing the target form.
LINKTOFORM() constructs a deep link to the form view named by view-name, followed by at least one column-name/column-value pair specifying a column name and its pre-fill value for the form, optionally in the app identified by app-id (or the current app if omitted).
AppSheet does not validate view-name, column-name, or app-id. If any of these are invalid (e.g., misspelled, or otherwise refer to something that doesn't exist), no error will be displayed.
AppSheet does not validate column-value. If a given column-value is invalid for the target column, no error will be displayed at least until the app user arrives at the target form.
Each of view-name, column-name, column-value, and app-id may be of any type, are interpreted as Text values, and will be encoded (as with ENCODEURL()) for use in the deep link.
An App value: the constructed deep link.