May the parties to a contract agree to refrain from filing an action for breach after one year despite the Florida 5 yr limit?

The parties may certainly make that agreement. They are defining how they will interact by the contract. They may be able to contest the validity of the clause for some reason or another, but in most cases, the court will uphold the agreement.
The parties may certainly make that agreement. They are defining how they will interact by the contract. They may be able to contest the validity of the clause for some reason or another, but in most cases, the court will uphold the agreement.