Everytime Transport For London takes money out of your main Monzo pot, it's backfilled by a separate TFL savings POT. At the start of the month fill your Transport pot to the top.
If
Any card purchase at a merchant
This trigger fires whenever you spend money at a particular merchant, and the transaction goes through.
Then
Move money out of a pot
This action will move money from a pot of your choice to your main account.
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