The order of the Input tables is essential. The top table reflects the Main flow connection, and for this reason, is given priority for reading and processing through the tMap component.
For this priority reason, you are not allowed to move up or down the Main flow table. This ensures that no Join can be lost.
Although you can use the up and down arrows to interchange Lookup tables order, be aware that the Joins between two lookup tables may then be lost.
Related topic: Using Explicit Join.