use a budget builder to generate the upcoming transactions (there’s a community solution Budget planner v2.0 that already exists and generates the list of transaction)
scan the list of generated transactions and sort them by month
match the expected transactions with the actual transactions from the transactions sheet
4)generate an enveloppe style tool (monarch does this) where you can create savings goal and then track all the balances in the accounts to make sure that future expenses will be funded (ie saving 300$ per week for a 1200$ monthly mortgage payment, etc)
Let me know if this makes sense. You maybe need a few new sheets to work. I see the recurring sheets transaction to be something like this.